This got me pretty alarmed:
I immediately checked the devices from which it was accessed but couldn't see any different from what I use usually. Nevertheless, even though I use two-factor authentication, I changed my password immediately.
Now, has any one of you had a similar experience? I thought the "problem" could be related with Google ignoring the dot (.) in the email thus for example firstname.lastname@example.org and email@example.com would come to the same email address. But, someone used the added numbers 33, so this hardly would pass as the same use case.
Anyways, still kind of baffled about it, so would appreciate some insight from more knowledgeable users.