What matters is taxable income, the amount reported on line 5b. The amount reported on line 5a is not involved in any of the calculations on your tax return. The amount on line 5a is only there to help the IRS determine if you have reported all of your Forms 1099-R. If the amount on line 5b is incorrect, either the payer reported something incorrectly on the Form 1099-R or you've entered something incorrectly into TurboTax.
