You cannot change it. Lots of people have made mistakes with that recovery rebate credit. The IRS is cross checking every return that has an amount on line 30 for that credit. If you really received an EIP payment that you put on line 30, the IRS will reduce your refund. Expect the mistake to delay the processing of your tax return.
If the amount on line 30 for the Recovery rebate credit is wrong the IRS will adjust it for you. You don't have to do anything. Did you claim too much for it? The IRS is reviewing all returns that have the Recovery rebate credit. There's been a lot of mistakes for that. If you tried to claim too much the IRS will reduce your refund or send you a bill.
@jaynamccauley Wait for your return to be fully processed and see what the IRS does with the incorrect amount you entered. If you have received less than the amount of stimulus payment for the 1st and/or 2nd EIP payments, then you will have to amend your return. But you cannot do that until your return has been fully processed.
Meanwhile...check your IRS account and see what the IRS shows for the EIP payments already made to you. And if you filed a joint return make sure to check for your spouse too.