I need help with the Math, PLEASE!

[LinusE]

I have checked the pair becoming set stats in 5 equal periods and they are between 8,4-10,4 % instead of 11,56%

If one look at the straigtdraw from flop to turn it is very close to hit a 6 rolling a dice 17% vs 16,7% and I would like to get some help with figuring out whay the chances are that if one roll a dice 486 times ( avg. should get 81 sixes ) one only get 40 sixes? How often or how many attempts rolling the dice( in series of 486 ) will one need on average?