When you enter the treasury bonds interest income as part of your Federal return, the interest reported in box 3 of your Form 1099-INT is automatically subtracted from your Virginia income. You can see this entry on the VA Form 760 as part of line 7 Subtractions. It is also reported on the VA Schedule ADJ.
If you are using TurboTax Online, you can pay to file your return and get access to review everything before you actually file.
Or, you can see a summary of the VA return by using these steps: