It will take IRS a few weeks to figure out it's impossible to adjust on their own.  They can find returns reporting unemployment, and they can find returns with a negative number on Line 8 of Schedule 1, but they can't automatically determine if that number relates to the unemployment received.  They can also match 1099-G data from states to returns, but they can't tell how much of it was already deducted on Line 8 (maybe the taxpayer had an NOL), and they can't recompute some of the other deductions and credits that depend on AGI.