When starting or ending an enrollment that is part way through the billing period, you will be prompted to prorate when you save their enrollment. You will be given three choices:
Use Default Prorate Amount - they will be charged based on the average cost per day times the days they are actually attending that period
Charge Full Amount - they will be charged the full amount for that period regardless of them starting and/or ending part way through the billing period
Override Prorate Amount - you can choose the amount you want them to be charged for this period