Sorry I still can't follow your amounts. Are you saying you already got $3,000 total for the first & Second checks? Then you should only have 600 on line 30. If you have 3600 on line 30 that is too much and the IRS will reduce your refund.
If you have not filed yet go back and enter the amounts you already got in the 2 boxes.
When you go through the federal review tab it will ask how much you got if any. 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." Say no to the amounts it shows you. Then 2 boxes will open up for each round. If you didn't get one enter a 0 in the box.
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.
