This is an impossible question to answer.
There are individual differences in addition to the fact that it is almost entirely based on environmental conditions.
If the animal is growing in normal proportions and there is no sign of any kind of imbalance, rate should not even be considered.
I've got tortoises that grow noticably quicker than others in the same group and there are many factors that could be the reason.
As to the amount you should feed... Let the tortoise decide. I feed more than they can eat. In the case of greens, I just leave it there until it is gone and then feed again. This sometimes takes a day or 2 and sometimes longer. The mazuri is the only stuff I take out after they have eaten their share.