If the member is delinquent (even by one day), the member is then in the next payment cycle (due date to due date).  Therefore, if the member pays the regular payment amount, the loan will advance the date by one period, or by two periods if the amount of the delinquent payment is double the regular payment that is scheduled.

For example, John Doe has a Overdraft Protection LOC account that is configured as single payment per period. At the end of September John is due for October 4. John does not make a payment until October 7 (he is technically 3 days delinquent when this payment is made). Because his payment is 3 days late, John is technically in his next payment cycle (due date to due date; in this case 9/4 to 10/4 was the first payment cycle, and 10/4 to 11/4 is the next cycle).  Any further payments after the delinquent payment date is made would advance the due date ONE more cycle. This is how a member's loan can advance 2 periods in one month, on a single payment per period loan.