Rating system for online games in Heroes of Might and Magic IV.

Maybe I'm misunderstanding something, but it seems to me that this is more of a performance statistic than a specific rating. It simply shows how many games have been played, how many wins, and how many losses. Or is it the same thing?
P.S. And to calculate it for many players, it's better to write formulas in Excel. That way, you won't have to bother the programmers. :)