My packing slip shows an ebay discount for the full amount of the sale. Will the buyer expect a refund?

The buyer used an eBay coupon when purchasing. eBay paid you what the buyer didn't have to pay. The buyer will already know they got a discount from eBay and the net is what they had to pay. I don't, however, understand how they got a full-sale discount unless they accepted one of those credit card promotions, which come with a nice signup bonus.