FYI. If you bypass the the credit card when adding the voucher, you can't place an order without adding it, even if the order is less than the $10 credit. i.e. can't use without adding credit card.
Ice creams were really good though.
Ah well that sucks. If they would only use google pay or paypal or something that lets me pay without sharing the card to them instead I would give it a go.
I have no faith in app developers to not lose the number and have to deal with getting a new card.