I know there was a thread about this awhile ago, and I DID LOOK BACK AND I FOUND IT LIKE A GOOD CHASEY but it got eaten (
http://z1.invisionfree.com/forums/DIVERGEN...showtopic=12076) and I can't remember what the answer was.
I was just cleaning out my inbox, and now I have negative space in my inbox (currently at -6%). What does this mean? Does this go away?
I'M NOT LYING. Here's a picture to prove it:

And yeah, I know one of those PMs is over 2 years old. I'm not deleting it. (:
I know EXACTLY what you're talking about. I don't have the picture, but on .hack//GL, another RP I'm on, I deleted a few PMs and ended up at -8. It was really weird. It's IF, for sure.
The problem here is that, very rarely, a PM will decay during deletion and release anticharacters, which take up negative space in your inbox. The chances are astonishingly small, but given how thousands of people are using PMs on this server every day, it must happen eventually. The more PMs you manage, the higher the chances of creating antibytes and anticharacters.
...
Okay, not really, but it sounded brilliant at first glance. In reality, this is a common board problem, especially when there are PMs from the time the server crashed. Sometimes the opposite happens. Some people have inboxes have ghost messages that take up space but cannot be removed. I think, in the end, it's simply that a message counter was somehow modified at some point and fell out of synch with the real amount of messages stored.
Regardless of the cause, IF is aware of this problem and has advised that people simply ignore the negative numbers because they can't do anything about it, and they're busy working out some future forum upgrades. For people with ghost messages, they can get a new account, or ask admins to raise the cap on their inboxes to a suitable amount. It can't be fixed permanently either.