Why is Turbo Tax Assessing a Prepayment Penalty?

I converted funds from my 403B to a Roth on July 7 and paid estimated taxes through the IRS website on August 2 (within the same quarter). But Turbo Tax is assessing me a prepayment penalty.  Why? I paid my estimated taxes properly but I don't think Turbo Tax asks you the date of the conversion so it must think I did it in an earlier quarter? How do I fix this? I don't want to have a penalty on record with the IRS when I did nothing wrong.