When you select the blue "Continue with Payment" button, the first donation prompt is for internal use only in case the customer offers a donation up front. The adopter should not be seeing your screen at this point:

When the checkout is texted to the customer for a credit card payment (or if you click "Use this device"), we will ask the customer for a donation on your behalf before they enter their credit card number:

However, if they offered a donation up front and you entered it into the first form above, we will hide this donation ask page from their checkout flow.

In the "use separate card reader/cash/check" flow, the team member processing the transaction would have to ask if the adopter would like to make a donation and enter it into the first form above. The adopter will not see a donation ask page at any point in this flow.