grenv: The figures are from the list of established players. Median would be a better word than average though I doubt the average would be much different. I'm not sure what effect the total number of games would have other than making for a smoother bell curve distribution.
I was also surprised when I saw how high the averages were. Compared to any other site these numbers are silly. At FIBS, for instance, average players are around 1500 and top of the range is 2000. At Vog its 1600 and 2050.