Auto debit will only take the fixed installment amount. You will need to check at branch to pay this. Alternatively, call them to ask whether it's ok to leave it there until you settle the final installment.

This is my assumption, and based on my experience when I wanted to pay the initial stamp duty + misc fees. I was given 2 options - pay at counter or pay during last installment when doing loan settlement, without incurring interest.

Your late payment fee may be a different case.

For auto debit, you cannot adjust the payment amount yourself, based on my experience. The system won't accept.