2 Discount Rates in Payment Terms Code

I need to create a Payment Terms Code that includes 2 levels of discounts.  2% at 15 days, 1% at 30 days, net at 31 days.  I set it up and ran the calculate function on the payment terms, and it appears to be correct, but when I create a voucher, it only sees the 2% discount, and pays the invoice in full after 15 days.  Could I be creating the terms code or the Voucher incorrectly?

Thanks,

Joe