Line 71 is not a field into which you should be directly entering an amount.
Line 71 on Schedule 5 (Form 1040) is populated with the amount that you indicated you will pay with your extension during the portion of the TurboTax interview in which you request the filing of Form 4868 Application for Automatic Extension of Time to File U.S. Individual Income Tax Return.
If you need to adjust the amount you will be paying, return to that section of the interview. Please do not override or otherwise try to force a result into Line 71.
