For this page I can see 13 comments in dashboard, but only 7 on the blog.
You have Google+ comments enabled for the blog. This means that if a person who leaves a comment on your blog has got their privacy settings such that only people in certain circles can see what they write, and you are not in one of those circles, then you will not be able to see the comments.
I agree that it seems mad that you cannot see all the comments left against your own blog posts. But that is how Google+ is designed to work. Some pepole choose not to enable Google+ commenting on their blog for just this reason: they stick to the standard Blogger commenting instead.