Average clutch sizes for ball pythons is around 6, but it can vary greatly. Some females will lay more smaller eggs and some will lay fewer larger eggs. No matter what though, the heavier the female the better your chances are of producing more eggs.

If you're growing up your own females, chances are they'll be smaller than a mature proven breeder female and therefore likely to lay fewer eggs... however, many females have laid big first clutches, provided they are a good size. I don't think anyone has gathered enough samples of clutch sizes to match them to any probability density function. I would just assume a normal distribution for now, meaning (given an average clutch size of 6) that a clutch will most likely consist of 6 eggs and any clutch size (either less or greater than 6) will decrease in probability the greater the difference is from 6.