While looking at someone else's reputation history recently I noticed the following anomaly -- the total for one day was +100, which is not the sum of the total activity for the day (+50 and +40). Since the day in question was a long time ago, I doubt that it's because of some pending action that hasn't been fully processed yet, nor do I think it's from a deleted post -- this particular user has made very few of them.
In short, it looks like simply a bug.
