Hi Tom.
Never mind going to FAQ. I can explain it. I'm clever.
Tomcr has five letters in it.
If you win a game you get +5 rating points,
If you lose a game you get -5 rating points.
If you draw then nothing gets added or taken away.
Weyerstrass the site's current No.1 has 11 letters.
He has won 394 games and lost 1.
so 393 * 11 = 4323
Take off 1882 which is his expected CFM (curve fluctuation manipulator.)
(far too complicated to go into great detail here - FAQ does not even mention it)
4323-1882 = 2441 which is Weyerstrass's current grade.
Hope this helps and welcome to RHP.