Ancient Exp

Anyone know what the deal is with ancient exp sometimes? Like the wild gray wolf ancient on 2x exp gets 129999 exp instead of 130000. There's a lot of other examples sometimes with even more exp differences, but this is the one I run into the most.

It's likely a precision error caused by too much floating point multiplication.

I'd explain it in more detail than that, but I believe Wikipedia has a nice article explaining the concept...