Apple Pay, your bank and the merchant use the secure encrypted digital device number. The number is unique to the device used to complete the transaction. The number used is displayed in your Apple Wallet app on the device used to complete the transaction.
Here is the path.
iPhone > Wallet app (not Settings) > tap card used for transaction > tap More button (3 dots in a circle in upper right corner of screen) > Card Number > Apple Pay
Only the last 4 digits of the encrypted device number is disclosed as a safety and security measure. Federal banking regulations say only the last 4 digits are required. Merchant or store manager should be familiar with the refund procedures.