How do I enter Virginia529 or Prepaid Tuition Plan details

Yes.  How much you can deduct depends on your age, how much you paid toward a prepaid tuition contract or contributed to a savings account this year, and if your payments to these accounts in a prior year were more than the maximum deduction allowed.

If the owner of the account is at least 70 years old this year, every dollar paid in a prior year that wasn't deductible in that year because of a maximum limit and every dollar paid this year is deductible. There is no limit.

If you're under 70 years old this year you can deduct up to $4,000 for each account you own. This dollar limit applies to current year payments and prior year payments available for a deduction this year.

Q. Would this involve adding the total contribution amount from 2017 to 2023 and subtracting the total amount that has been deducted for the tax years 2017 to 2023?

I'm not specifically familiar with the VA software.  But, based on the software for other states, you don't do any subtraction. You enter both numbers and let TurboTax do it's thing. It will give you the maximum 2024 deduction and carry over the new balance to next year.