In fact, the worksheet is calculating your amount correctly.
According to the New for 2021 section of the IA 1040 Income Tax Return Instructions,
Economic impact payments (EIPs) whether in the form of a rebate or refundable tax credit will not be included in Iowa taxable income, or added back as part of your reportable federal income tax refund.
And later, in Step 7 – Federal Income Tax Refund / Overpayment Received in 2021, the taxpayer is instructed not to include the amount of Economic Impact Payment (stimulus payment) in the federal refund amount.
