Turbo Tax calculated the incorrect taxable amount on the 1040 line from an OPM (federal) 1099-R entry, which is different from the 1099-R. Info entered correctly. Why?

I entered the gross distribution and the amount in box 2a. shown as the taxable amount, along with the total employee contribution in box 9b.  TT calculated the taxable amount $95 lower than shown on the 1099-R for some reason - totally ignoring what I entered as the taxable amount.