Tax rate is computed in error on Form 1040, line 16 when lin 17 has a number.

This issue is on Form 1040, line 16. If you look at the worksheet for tax rate, it calculates $313 tax when taxable income is $75,544 on line 15,  Form 1040. This could happen when line 17 has a number of $7947.  Line 16 tax should be $8,652. Wonder how $313 is calculate.