Conversion Timing with CB Card

self.AMPToken2m ago
So I try to use my Coinbase card as often as possible and get my 4% back in Amp. My question is the following.... When a transaction is not instant and states that it is "pending" and then tells the "estimated rewards" when is the estimated reward converted into amp? Is it whatever the price of an amp token was when the transaction was first initiated or is it converted to amp based on the token price at finality and it is no longer pending? Right now this is not a big deal with the current price of Amp token, but there could be some huge swings during a day or two of pending time in the future