第一次还车贷，
看见两个选项：
Standard Payment
Applies to both principal and interest
Paying more than the standard monthly payment may reduce the amount due on
your next invoice.
To payoff your account, enter the estimated payoff amount above.
和 Principal Payment
Applies only to the principal balance
Making a principal payment does not reduce the amount due on your future
invoices
Cannot be made if a payment is past due
为啥Principal Payment “does not reduce the amount due on your
future invoices” ？
