Why is TT calculating estimated tax when my prior year tax refund will be carried over to current year estimated tax payments & more than covers what I will owe?

Taxable income about the same, premier edition, was going to take a partial refund & leave refund balance of a little over what I expect to owe.  Then, decided to leave in total refund when TT calculated that I have to pay additional estimated tax almost equal to the partial refund I was going to take.  TY.