This needs clarification:
1. You need to activate an Amex Points promo
2. Depending on your personal offer, you might get 50% off an order with a $80 maximum, or 40% off an order with a $40 maximum
3. Works on any set, not just the A-frame, so this is not set specific. A-Frame is just an example of how to maximize the promo.
4. Does not work for everyone, and not for every Amex card.
TL;DR: YMMV