niel2k, to summarize what kate3116 said, because you will be receiving the corrective distribution in 2020, long after the due date of your 2018 tax return, and are required to pay 6% excess contribution penalties for 2018 and 2019, the corrective distribution is simply a distribution of your $5,500 excess only. No earnings need to be distributed.
The amendment to your 2018 tax return is to add 2018 Form 5329 to calculate and pay the 6%, $330 excess contribution penalty on the $5,500. You'll have the same penalty on your 2019 tax return because the excess was not removed before the end of 2019. The regular distribution of $5,500 that Vanguard indicated will eliminate the excess when you file 2020 Form 5329 with your 2020 tax return next year.
