What is it based on? Logs? Do you upload a Simcraft to the site?
I'm Fury but I'm still listed as Arms. No idea how it works.
It checks your armory and simcrafts. For obvious reasons it isn't constantly updated.
It runs a patchwerk sim with 100 iterations and default settings.
It's better than raw ilvl to compare the potential of two characters of the same class/spec and that's about it.
Well again it's just using some spare power to let those sims run for giggles. It should be quite obvious that these can't always be updated instantly.
It seems to be updated now. Currently shows you as Fury, last calculated as of 4 hours ago. Still shows you below a number of people that you "outgear". Interestingly enough, the only warrior with a higher ilevel than you is also below those same people (he's 4th to your 5th in SimDPS rankings).