You only enter the 2019 AGI at the end to verify you to efile. Where else are you seeing a place to enter it? You don't enter the AGI in the Recovery rebate credit section.
Just enter the amounts you did get and if you qualify for more it will be added to 1040 line 30.
Forget about 2018 and 2019. The Stimulus Checks are really based on your 2020 return we are filing in 2021. So any amount you already got will be reconciled on your 2020 return line 30. If you didn't get a Stimulus Check (and qualify) or you qualify for more it will be added to your 2020 return. But the good news is if they paid you too much they won't take it back.
When you go through the federal review tab it will ask how much you got if any. Enter a 0 in the box if you didn't get one. Or to enter your stimulus payment in TurboTax, type "stimulus" (without the quotes) in the Search box, then click the link that says "Jump to stimulus."
After you have entered your tax information and are ready for the Federal Review, it will be the first question.
If you are trying to trigger it, you can go to Other Situations, answer any questions and click Done. The next automatic selection is Federal Review and it will ask about payments received.
