If you go to the Form 2210 and follow the "worksheets" and "zoom" button by the side, you should be able to see how to final penalty is calculated. At least, it did it for me after I entered everything using the Interview Step mode first and then switched to Forms to check at the end. Note: I trusted that TurboTax had their numbers, periods, rates, etc. correct. But you can see how they calculated your final penalty there.
