Fidelity GPOS using MCR to invoke Discount

I have a GPOS ECR, I have setup a 10% discount on food, but I want invoke it using a customer swipe card, I have found the scanner rules and understand the first part of the prefix, but how do i link up a card I know 6 denotes discount. So if i wanted to get some cards programmed up to use discount number 1 what should I get programmed on the cards and what do I set in the scanner rules. Thanks in advance.

Adrian