Help with 1040X line 13-22

[Gnart]

I need to file 1040X to amend the amount of tax withholding. I excluded tax withheld on an item. On line 1-11, data came from the original 1040 since there was no change. On line 12.A (original 1040, ie:5000), 12.B (increase, amount I shorted myself, ie:400), 12.C amount A+B (ie: 5400). I read and could not decipher the instructions for line 13 through line 22. I am looking for help as the number to put in line 13 - 22 to get refunded, presuming that I mailed the IRS a check for $1000 with the original 1040 to pay for the deficit.

Thanks

[Critter]

Ok ... this is an error the IRS usually catches for you ... when did you file the return?   If it was less than 10 weeks ago you should do nothing and let the IRS fix this issue for you.  

[Critter]

https://www.irs.gov/pub/irs-pdf/i1040x.pdf