Coach--you are not playing 1 million different hands. You are playing only 10,000 different hands, and therefore any deviation in the variance is not spread over as many applications and thereby skews the results. You could also get a deviation in which you get bad hands over the shorter term, and skew the other way. But the whole idea of a million or 10 million DIFFERENT HANDS is that it evens out. 10,000 is not nearly enough.