On the Sponsorship Details page, in the Current Pledge Balance section, the Balance is the amount that will be remaining at the EOM closing of the current month. The Balance is available to cover future months' support. Divide the Balance by your monthly support amount to determine how many months will be covered before you need to send more money.
If you are paying quarterly, semi-annually, or annually, you will receive a reminder letter that it is time to send more money or that a withdrawal will be made for AutoPay. If you pay monthly, your receipt is your reminder to pay the next month.