Tax Calculation

I (as others) am seeing an issue with TurboTax calculating the tax as it relates to my taxable income. I have a spreadsheet set up to calculate the tax via the tax brackets and I also did it using the other method of taking your taxable income multiplied by the bracket percentage, and minusing the constant in the table. Those two methods come up with the same number. But, the TurboTax calculation for line 16 is $58 less. Not a big difference, but my expectations are they should all be the same...so why is TurboTax not the same??