Did you enter the withholding when you entered the 1099G?
To enter withholding on Unemployment:
After you enter the Payer's name & address then on the next screen you select your state and enter the amount of Unemployment, there is a checkbox that says "Federal or state income tax was withheld on this payment". You have to check it for the withholding boxes to show up on the next screen.
Federal withholding is shown in box 4 of the 1099-G and state withholding in box 11. If you entered the 1099-G, as shown, in TurboTax (TT), TT picked up the withholdings and entered them in right place on the forms.
The amount on line 25a of form 1040 is the total all federal withholding from all forms (W-2, 1099-G, 1099-R, SSA-1099, etc).