The TT program ( and my professional program as well ... this is not just the DIY programs where this happens) figures the ESTIMATED underpayment penalty based on the info you entered in the program however the fed/state have the right to calculate the penalty based on the info they have on file and the date you make the payment ( TT assumes you will pay on the last day of filing season ... if you pay earlier then the amount could be less) and the amounts are not always the same so enjoy the refund of the excess penalty. In the future you can override the estimated penalty if you wish and wait for the IRS/State to bill you instead.
