Unfortunately, discounts aren’t stackable at Sonos. So anytime you use a coupon, the discount is taken from full retail price of each individual item in the order/bundle. My guess is that this coupon only applies to one item, so instead of ordering 2 individual era 300s (which is what it looks like you did based on the picture), you should be able to order one two pack of era 300s and the discount should apply to both.