The document describes the user's mental model and the implemented model for transferring money between accounts using an ATM. The user's model involves confirming a request, entering the account number to withdraw from, entering the amount to transfer, and entering the account number to transfer to. The implemented model is represented as a state transition diagram showing the steps of swiping the ATM card, entering the PIN code, entering the amount, entering the account number to transfer to, verifying the transfer, and ending the transaction.