Starting in 2018, the state of Ohio has doubled the available deduction for residents from $2,000 to $4,000 per year.
The maximum contribution limit is $4,000 per beneficiary. If you are entering $5000 per beneficiary, TurboTax is giving you the maximum of $8000.
You may have carry over from previous years. You are allowed $4000 per kid. 4000 x 2 = 8000. $5000 this year plus 3000 carryover = 8000.