There are 552 spots, so 500 for the main game, 52 for DLC.
These were the entries bumped out of the game because they were at the end of the file. The game loads entries until it runs out of room and anything leftover is just ignored.
So I checked out the new character.xtbl included in today's patch_compressed.vpp update, and you guys seem to have dumped all the DLC character entries into character.xtbl...what's the reason for this move?