Promo code cashback is cashback obtained from cashback promo code campaigns and are usually valid for 30 days unless stated otherwise. The promo code cashback amount rewarded will be calculated based on the final transacted amount of a purchase (i.e. after deducting any existing cashback used in the purchase).
Here is where you can get more information on where to check on your existing cashback. Remember to use your rewarded cashback before its expiry so that you can make the most of your reward!