You cannot do a 2018 Form 1099-R for a distribution in 2019. Because it's late to do a return of contribution of any more of your 2017 contributions before the due date of your 2017 tax return, you are stuck with excess contribution penalty for 2017 that resulted from the increase in income on your 2017 tax return caused by the earnings reported in box 2a of the 2018 Form 1009-R that you already have and, if you can't apply this excess carried into 2018 as part of a 2018 Roth IRA contribution, you'll have another 6% penalty for 2018 on this remaining excess.
To avoid another penalty for 2019, you'll either need to be able to apply it as part of your 2019 Roth IRA contribution or obtain a *regular* distribution of the excess, with no adjustment for earnings. Since it comes from your Roth IRA contribution basis, the regular distribution won't be taxable or subject to penalty. You'll report that distribution on your 2019 tax return and it will appear on line 20 of your 2019 Form 5329.
