After you file

Sorry but you are not understanding. You don't get the 600 twice.  The IRS already gave you a deposit for it and your return  tried to claim it again on line 30.  

 

We know it should not be on your tax return.   But it was and it REDUCED your real tax due to $1.  So if you take it off your tax return you don't get to reduce the tax due you would have had.