Total withholding amounts

The amounts from your W-2 box 2 and on the Form 1040 Line 25a should be the same.

Look to your Form 1040

You can view your Form 1040 plus Schedules 1, 2 and 3 at any time using the online editions. Click on Tax Tools on the left side of the online program screen. Click on Tools. Click on View Tax Summary. Click on Preview my 1040 on the left side of the screen.

You might be adding up the wrong withholding on your pay stubs.   It's only the federal income tax withheld.  Not state withholding or FICA (Social Security & Medicare).