Originally Posted by Rare

$5 once per month. It can accumulate up to $15. Any accumulated amount can be used on the same order.

In my case, I received $5 credit in April and another $5 in May (received emails about them on April 4 and May 2). Last week I used $6.05 toward one order, stacked with a 35% off coupon code; the app says I have $3.95 left.