When a payment is made on your Tenet Dashboard, it applies to your loan balance in the following order:
Unpaid fees (Late fees may be applied if Loan is 10 Days past due).
Accrued & Unpaid interest.
Due principal.
If you make a payment that covers more than the upcoming Monthly Payment (Due Interest, Principal, & fees), the extra amount applies toward your loan principal (If Portion of Principal was deferred, then will apply toward deferred amount first), which will lower your overall interest on your loan. And depending on how much interest is lowered, may shorten your loan term as well.
For example: Lets say your Monthly is $500/Month, and by paying off the Deferred Early, you saved yourself $1,500 in interest, you would lower your loan term by 3 Months.
If you would like to make a payment towards your Loans Principal instead of The upcoming Monthly Payment, mark off "Apply this payment to my remaining principal balance", when Making a Payment.