Code Q indicates that your Roth IRA distributions are qualified distributions, so there is no need to enter the amount of your past Roth IRA contributions. That amount is only needed when preparing Form 8606 Part III and you no longer file Form 8606 Part III once you've met the requirements for qualified Roth IRA distributions. You can enter any number you like or leave it blank. It won't get used in preparing your tax return.
