Form 1040 Schedule 1 Line 18, how to clear it?

Upon "Federal Review" an error was flagged and it showed me Form 1040 Schedule 1 and only Line 18 was editable.  I entered the value the error indicated just to placate the checker (knowing full well the value in the indicated field was incorrect but assuming I could "go back later" and correct it).  Here I am, needing to get back in and edit Form 1040 Schedule 1 Line 18 but can't.

 

I've checked all of my HSA work, IRA contribution activity, and 1099-DIV/1099-INT numbers, none seem to correspond to the number appearing on line 18.  A hack would be to enter Form 1040 Schedule 1 Line 24z to "reverse" this number (enter a negative value) so that they zero out, but I can't even find a way to enter Income Adjustments to do this.

 

So, Form 1040 Schedule 1 Line 18 has a value in it that I would like to zero out.  How do I get to a screen that allows me to do this (Turbotax online)? 

 

Thank you very much.