i wasn't sure what the #'s mean either...
i think they have to do with the hand position.. notice the numbers go up, so it has to do with the bevels... sampras/henman palm is square to racquet, nadal is under the racquet (or something like that).
article sounds interesting.... my forehand has been screwed up before because stance didn't match the grip. and it wasn't that easy to fix. i often have that problem when i haven't played for a month.