You get the recovery rebate credit if you did not receive stimulus checks, or if you did not receive the full amount that you are entitled to. Since you did get the checks, you already got all the money you are entitled to, so you do not get the credit on your tax return.
Form 1040 line 30 is not the amount that you received. It's the amount you did not receive, but should have received. If you received the full amount that you were entitled to, then there is nothing on line 30.
