Did you enter any capital gains or qualified dividends on your tax return? If so, your taxes on taxable income are not calculated using the IRS tax tables but the Qualified Dividends and Capital Gain Worksheet.
Go to the IRS Form 1040 Instructions for the QDCG Worksheet page 36 - https://www.irs.gov/pub/irs-pdf/i1040gi.pdf#page36
