When it comes to the codes in box 7 of a 1099-R that you were issued, you don't get to chose or change what the issuer of that 1099-R put in that box. So I'm not understanding why you're concerned with this now, since you will not receive the 1099-R for the withdrawal until 2020 anyway.
Or are you trying to show this on your 2018 return? If you do show it on your 2018 return, understand you're going to compound things for your 2019 taxes. That's because you will receive a 1099-R for the 2019 withdrawal, regardless of the reason for the withdrawal. So I would highly suggest you wait and report it on your 2019 tax return.
