So at first I thought it was a great feature when they added the ability to see what monsters might drop in a dungeon, rare drops etc. But with the recent renewal of the old dungeons, I've noticed that they don't display every floor/drop, and the "+?" box also never seems to fill up (I used to think that +? box was for rare invades I'd not seen, but I don't think that's true). If nothing else, what is that +? box for?