Originally Posted by Fat the kbxe
I seriously don't understand that system.
This means that just because some Pokémon like for example Latios isn't used much, then it ends in UU? Can Latios be in UU? No. So this system doesn't seem to be working well does it?
UU stands for Under-Used. That means it isn't used as often as the Pokémon in OU (Over-Used). If it's too powerful for UU, but not popular enough for OU, then it goes to BL. So yes, that's exactly how it's supposed to work.