Our store is going to offer people with a coupon code one free product of their choice from a selection of products. I've created the coupon, entered the ID numbers for these products, and have set the coupon parameters for "Expires After One Usage By Each Customer." But a test reveals that the store wants to give customers as many of these identified products for free as they add to cart. I thought the store would assign the coupon to the first product and charge the proper price for each added product after that. How do we get the cart to only assign the coupon to that first choice?