Amex Card Members who purchase with a qualifying Amex card will $50 statement credit after their $100 purchase. There is no checkout integration at all, so you will not see the $50 off during checkout. Amex will bonus based on the final amount charged to the customers Amex card – if this final charge is at least $100, Amex will issue the customer a $50 statement credit.
The statement credit is based on cumulative spend during the campaign period. So if a Card Member spends $50 with us one day and comes back and spends another $50 with us another day (or any amounts totaling at least $100) – Amex will issue the statement credit once the customers total cumulative spend with us reaches the $100 threshold.