Hmm... Since Jacob made the Fakku Books section count as well, I get the feeling that he might have recalculated out post counts, but thereby removed the bonus 150 we got for one of the rollbacks...
Also happen to me and Odamust too, at least. Though, the numbers of lost posts are varies (he loses like 50, while I lose 156). Maybe as Luin-san have said.
As has been hinted at I recalculated all the user posts, it should actually be 100% accurate now unless I got my code wrong. I'll double check now and make sure.