You do not enter anything on a Form 1099-R if you did not receive a 2021 Form 1099-R. Delete the form you started and when asked if you received a Form 1099-R answer NO. Then answer YES to the questions for receiving a disaster distribution. Then you can enter the amount of the 1/3 of the 2020 distribution in both boxes for Line 9 if the 2020 distribution was from a 401(k) or both boxes for Line 17 if from an IRA.
