The following is the comment the original poster made to the answer given to @FullDecent:

Thank you for your answer. However, I've got a custom made label that has 1 unread message and the unread count is 0! – Eliyahu Feb 12 '14 at 15:07

I believe the original poster has found existing inconsistencies with the way Gmail handles messages and conversations and labels and their user interface.

Short explanation

1. Gmail searches internally first get a bunch of individual messages.
2. They then show you only those conversations that have those messages that individually satisfied the search criteria.
3. Gmail does not classify new message in a conversation with the existing user labels of the conversation it belongs to.
4. The result is that fewer conversations are found and presented than users expect.

More detail

I suspect you're seeing the result of this Gmail bug. It may be that the conversation under that label has only some of the messages actually with that label.

And the new (unread) message in that conversation has not yet been labeled automatically (that's the bug). The result is that the single message is "unread" but does not have a label.

So if you search for "is:unread label:mylabel", then it finds messages that are simultaneously unread and labeled "mylabel" and then it presents you with the conversations that have those messages.

Since the new (unread) message is considered unread by Gmail, that conversation is not shown in the search results.

Some references:

See obscure Gmail docs that say:

When you add a label to a conversation, it only applies to the messages already in that conversation – not to messages sent after you applied the label. When you search for labeled messages, you'll see any messages that match the label, along with their conversation thread. However, you won't be able to search for an individual message in the thread that doesn't have that label.

And a blog post discussion.

Also lifehacker.

StackOverflow.

The following is the comment the original poster made to the answer given to @FullDecent:

Thank you for your answer. However, I've got a custom made label that has 1 unread message and the unread count is 0! – Eliyahu Feb 12 '14 at 15:07

I believe the original poster has found existing inconsistencies with the way Gmail handles messages and conversations and labels and their user interface.

Short explanation

1. Gmail searches internally first get a bunch of individual messages.
2. They then show you only those conversations that have those messages that individually satisfied the search criteria.
3. Gmail does not classify new message in a conversation with the existing user labels of the conversation it belongs to.
4. The result is that fewer conversations are found and presented than users expect.

More detail

I suspect you're seeing the result of this Gmail bug. It may be that the conversation under that label has only some of the messages actually with that label.

And the new (unread) message in that conversation has not yet been labeled automatically (that's the bug). The result is that the single message is "unread" but does not have a label.

So if you search for "is:unread label:mylabel", then it finds messages that are simultaneously unread and labeled "mylabel" and then it presents you with the conversations that have those messages.

Since the new (unread) message is considered unread by Gmail, that conversation is not shown in the search results.

Some references:

See obscure Gmail docs that say:

When you add a label to a conversation, it only applies to the messages already in that conversation – not to messages sent after you applied the label. When you search for labeled messages, you'll see any messages that match the label, along with their conversation thread. However, you won't be able to search for an individual message in the thread that doesn't have that label.

And a blog post discussion.

Also lifehacker.

StackOverflow.

The following is the comment the original poster made to the answer given to @FullDecent:

Thank you for your answer. However, I've got a custom made label that has 1 unread message and the unread count is 0! – Eliyahu Feb 12 '14 at 15:07

I believe the original poster has found existing inconsistencies with the way Gmail handles messages and conversations and labels and their user interface.

Short explanation

1. Gmail searches internally first get a bunch of individual messages.
2. They then show you only those conversations that have those messages that individually satisfied the search criteria.
3. Gmail does not classify new message in a conversation with the existing user labels of the conversation it belongs to.
4. The result is that fewer conversations are found and presented than users expect.

More detail

I suspect you're seeing the result of this Gmail bug. It may be that the conversation under that label has only some of the messages actually with that label.

And the new (unread) message in that conversation has not yet been labeled automatically (that's the bug). The result is that the single message is "unread" but does not have a label.

So if you search for "is:unread label:mylabel", then it finds messages that are simultaneously unread and labeled "mylabel" and then it presents you with the conversations that have those messages.

Since the new (unread) message is considered unread by Gmail, that conversation is not shown in the search results.

The following is the comment the original poster made to the answer given to @FullDecent:

Thank you for your answer. However, I've got a custom made label that has 1 unread message and the unread count is 0! – Eliyahu Feb 12 '14 at 15:07

I believe the original poster has found existing inconsistencies with the way Gmail handles messages and conversations and labels and their user interface.

Short explanation

1. Gmail searches internally first get a bunch of individual messages.
2. They then show you only those conversations that have those messages that individually satisfied the search criteria.
3. Gmail does not classify new message in a conversation with the existing user labels of the conversation it belongs to.
4. The result is that fewer conversations are found and presented than users expect.

More detail

I suspect you're seeing the result of this Gmail bug. It may be that the conversation under that label has only some of the messages actually with that label.

And the new (unread) message in that conversation has not yet been labeled automatically (that's the bug). The result is that the single message is "unread" but does not have a label.

So if you search for "is:unread label:mylabel", then it finds messages that are simultaneously unread and labeled "mylabel" and then it presents you with the conversations that have those messages.

Since the new (unread) message is considered unread by Gmail, that conversation is not shown in the search results.

Some references:

See obscure Gmail docs that say:

When you add a label to a conversation, it only applies to the messages already in that conversation – not to messages sent after you applied the label. When you search for labeled messages, you'll see any messages that match the label, along with their conversation thread. However, you won't be able to search for an individual message in the thread that doesn't have that label.

And a blog post discussion.

Also lifehacker.

StackOverflow.