Your affiliate account will have a negative balance if your customers win more than they lose. This may happen from time to time but generally the collective Sports, Casino, Poker, Games and Bingo balance will be positive.
For example, in month 2, your affiliate account might show negative earnings. You would not be asked to repay your commission from the previous month to offset this balance, however, you would be required to wait until new customers (or new activity on existing customers) results in positive net revenue for you to receive your next commission payment.
Your commission is a percentage of the net profit on your customers. If your net profit is negative or drops below what you have already been paid, you will not receive a new commission payment until your account balance returns to a positive position.