Well withholding would come from W2 box 2 and any 1099 box 4 and from Social Security SSA-1099. Check all those, add them up. Maybe you imported a form and also manually entered it? Maybe you entered a decimal point in the wrong place or left it out. It's easy to make a typo.
For importing investments you still need to check it over before filing. It might have imported wrong. It's not always accurate.
