in the real world, like a store you physically walk into & have the ability to talk to the store manager kind of place, the business will typically acknowledge the mistake & extend the coupon in favour of the more all-encompassing statement, meaning that everyone should be allowed to use the coupon, regardless, because of the wording. and/or, they would refund or offer credit to those folks who tried to use the coupon under confusing/mis-leading terms and were denied usage yet made a purchase anyway [though the latter, admittedly, and honestly, is far more of a managerial discretionary decision]. having spent far too many years in retail, and i've yet to find a company who didn't utilise 'good faith' practises in one way or another in order to maintain that all important customer retention.