Why Turbotax charge me almost 500 dollars more tax, how did they calculate your tax using tax computation worksheet

If your income is over 100,000, then use tax computation worksheet to calculate your tax.   Why the tax amount in Turbo Tax is more than the one on IRS web site?   I have the taxable income number from line 15 which is after the deduction.   but if I am using the formula on  IRS web site, it is much less then Turbo tax told me.  something is not correct in the Turbo tax.   Why?