It has to do with your relation to the rest of the league over the last 15 days. I would have to assume it is your z-score in each category in relation to the league average or something. There is a lot of uniformity in the counting stats because there are a limited number of possibilities.
They take each of your categories and make a total out of it. For example, his 2.35 R would be a z-score of runs compared to the league mean.
Take Justin Upton on the season long Player Rater:
I made up the standard deviation, but I want to think it is right. It makes sense anyway.
Sorry Zombie for making it even more boring.
This post was edited on 4/22 at 10:18 pm