Real Estate Mgmt - PAYMENT METHOD (LEPM) - Advance vs. Arrears

Working with a client and setting up the BSLA (Balance Sheet Lease Accounting) method. In the recurring billings is a field called PAYMENT METHOD (LEPM). The options are IN ADVANCED and IN ARREARS. I am unsure how (or if) this field has any effect on the amortization schedule that is created during BSLA. My client is expecting it to have an effect, I have run several scenarios with the same data but changing that field with no change of results. Just need a good idea of what the PAYMENT METHOD field does.