AFAIK I haven't had any payments due as a student.
Description of interest rebate FYI:
Interest Rebate Amount - This is the amount of an up-front interest rebate that you may receive as part of a program
to encourage the timely repayment of Direct Loans. If you receive a rebate, the Interest Rebate Amount will be added
back after the Loan Fee Amount is subtracted.
To keep an up-front interest rebate that you receive on your loan, you must make all of your first 12 required monthly
payments on time (we must receive each payment no later than 6 days after the due date) when your loan enters
repayment. You will lose the rebate if you do not make all of your first 12 required monthly payments on time. This
will increase the amount that you must repay.