Yea each staff category can access different post as in there are post that only admin can access, just an example. I may be wrong on this assumption but that's what I think.
I marked "ban appeals" read and it dropped to 236. Edit: 10 more thread appeared on the "New Posts" page. They weren't there before. Read, down to 133. Edit2: Random old threads were appearing on the page, one by one (I'm using chrome, not Internet Explorer, so this is pretty weird). Down to 126 Edit3: I marked the entire Private Complain/Ban-Appeal/Bugs Section read and now the number is a 0.