the idea is: you can't return a thing until you get a refund card, which lets you return it (good for one use only.)
Here's a scenario:
you get a $50 bike. you can't wait to ride it so you do right away (of course taking necessary precautions). You only, however, ride for 5 minutes. why? because it suddenly broke. it was quite the setback. you go back to the store to return it, but you can't because you're out of refunds, so you buy a $10 refund card, letting you return the item, getting back $50 (or $40 if you factor in the refund card)
TL;DR:
you buy thing, thing breaks, you can't return thing, you buy refund, you can now return thing.
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