I don't think it will impact the tax.

Make the change to the 1099R and see if the taxes change at all.  You will need to go through the questions that follow the 1099R.  If there is no tax change then no need to Amend.

To EDIT pension and annuity Payments (1099-R)

•    Click on Federal Taxes
•    Click on Wages and Income
•    Click on I'll choose what I work on (if shown)
•    Scroll down to Retirement Plans and Social Security
•    On IRA, 401(k), Pension Plan Withdrawals (1099-R), click the start or update button, then make the change and answer the questions again.