Turbotax 2019 calculated long term capital gain tax at 24% instead of 20% - wrong?

I am puzzled by Turbotax 2019 for home and business.

 

If I artificially remove a long term capital gain item (stock) by reporting sales proceed same as cost basis - the gain was $26733, my fed tax would drop $6436. It means TurboTax is calculating the rate on capital gain as 6436 / 26733 = 24%. It is supposed to be 20% at most.

 

I checked the imported 1099-B forms, those long term items are indeed marked as "L".

 

Checked Qualified Dividends and Capital Gain Tax worksheet. it appears 20% was used to calculate the capital gain tax. 

 

But why the final result is 24%, instead of 20%...