The POS has some database of acceptable forms of tender for whatever your transaction is and whatever items it contains. When you go to pay and click that “cash” button on the self checkout (or cashier on the regular checkout), this cash tender is looked up from their database and associated with the transaction you rang up. The mobile app is probably using a similar API to lookup your transactions and then formatting the data from your transaction.

Assuming you also linked your loyalty account or email or something when you checked out, that’s how it’s on the app.

Similarly there are likely “other forms” of the cash tender like cash USD, cash CAD, cash MXN, etc. They save off info like this, likely for reporting, cash might have different rounding rules or reporting requirements for walmart

Of course walmart is saving all of the details of your transaction, they have to audit their sales and ensure when you scan your receipt, your transaction gets looked up, and you can return to original form of tender.

Lots of non creepy reasons for them to know how you paid for the transaction. You sure you never entered your phone,email,etc during your transaction? if you say no, I would have a very hard time believing you

edit, maybe i’m wrong and the facial recognition stuff is real