The IRS will adjust it. The IRS issued guidance March 1, 2021 regarding this situation. There will be a slight delay in processing your return.
2020 Recovery Rebate Credit — Topic G: Correcting issues after the 2020 tax return is filed
DO NOT file an amended tax return with the IRS. If you entered an amount on line 30 but made a mistake in calculating the amount, the IRS will calculate the correct amount of the Recovery Rebate Credit, make the correction to your tax return and continue processing your return. If a correction is needed, there may be a slight delay in processing your return and the IRS will send you a notice explaining any change made.