To pay deposit only ($525), by default Puppy Deposit is selected and checked, so just uncheck the Remainder (Final) Payment.
To pay for the puppy in full, Deposit ($525) and Remainder (Final) Payment (2,975), for a total payment of $3,500, both boxes should be checked so make sure they are.
If you have already paid the Deposit ($525) and are coming back to complete the Remainder (Final) Payment ($2,975), uncheck the deposit box and make sure the Remainder (Final) Payment is checked.
Finally, please ensure your total is correct before you enter your credit card.