TurboTax is asking for the year-end value in your own IRAs, not the inherited IRA. The year-end value in the inherited IRA is to be entered nowhere in TurboTax. The taxable amount of the distribution fro the inherited IRA must be done on a separate Form 8606 outside of TurboTax and only the the resulting taxable amount provided to TurboTax. TurboTax can only handle your own Form 8606, not a Form 8606 for an inherited IRA.
You should include the separately prepared Form 8606 with your printed and mailed tax return.
