I'm at the center of a 3x3 square fog cloud. I've got full concealment from those outside the cloud, but would a creature outside the cloud have concealment or full concealment from me?
unless you have some ways to see through smoke...yeah they have total concealment.
I ask because there seems to be a consensus that, when you're standing in the very edge of a fog cloud, you get concealment but your enemies outside the fog cloud do not. That seems to imply that you don't count your own square.