i dont think he clearly explained the halacha unless he meant somthing other than i understood
+1
The question of how much you need to tell them to make it not "tricking them" is still unclear.
The standard psak in this case is that you can take advtange of the store's policy, even if it doesn't make sense. However, it is still not clear in what circumstances you can assume their policy.
Is the fact that the computer does not take money off the return enough to confirm their policy?
They can see the entire order on the computer, is that enough?
Is giving them both recipets enough?
Or, do I need to give them both reciepts and point it out?
This is the follow up question which is needed.