Using Confluence Server 6.2.0.
Add an attachment with label first.
Add the same file again with label second.
So far so good. Both versions show up and the "top" one has the correct label of second.
Add the same file again with label third.
Now two version 2s show up.
Add the same file again with label fourth.
This version does not show up in the list at all.
So I am guessing something is really broken with attachment versioning?