where does the other 200 go?

It's difficult to determine exactly where the remaining $200 is going without more information about your auto loan. However, there are a few possibilities:

1. Interest: A portion of your monthly payment goes towards paying the interest on the loan. If your loan has a high interest rate or a long repayment term, it's possible that a significant portion of your payment is going towards interest.
2. Fees: If your auto loan has any fees associated with it, such as late payment fees or origination fees, those fees could be reducing the amount of your payment that is applied to the principal.