Line 28 would be the child tax credit for the new baby on 12/30/2021.
What it sounds like may have happened is that you reported that you had not received any of the recovery rebates (stimulus). Letter 6475 would have told you what you received in stimulus credit. The amount of recovery rebate for you and your wife would have been $2,800.
The IRS is verifying the recovery rebates before issuing refunds. Most likely when your return was processed it was discovered you had already received the recovery rebate and that amount was deducted from your refund.
