From Pub 1345 page 17 (PDF page 21):

Taxpayers must sign a new declaration if the electronic return data on individual income tax
returns is changed after taxpayers signed the Declaration of Taxpayer and the amounts differ
by more than either (i) $50 to “Total income” or “AGI,” or (ii) $14 to “Total tax,” “Federal income
tax withheld,” “Refund” or “Amount you owe.”