Are you referring to the two lines on the screen entitled "Let's enter your HSA contributions" (see screenshot below)?
The first line should be the same amount that is on your W-2 in box 12 with a code of W. It is not editable - because you should edit it on the W-2.
The second line is the amount of your "personal" contributions, that is, amounts paid directly to your HSA administrator, NOT through a payroll deduction plan. If you have any, this is where you enter it.
If you believe that the amount displaying on this screen in the first line does not match your W-2, then the best way to fix this is the following:
The safest - although brute force - way to fix this is to do the following:
1. make a copy of your W-2(s) (if you don't have the paper copies)
2. delete your W-2(s) (use the garbage can icon next to the W-2(s) on the Income screen
*** Desktop***
3. go to View (at the top), choose Forms, and select the desired form. Note the Delete Form button at the bottom of the screen.
*** Online ***
3. go to Tax Tools (on the left), and navigate to Tools->Delete a form
4. delete form(s) 8889-T, 8889-S (if one), and 1099-SA (if one)
5. go back and re-add your W-2(s), preferably adding them manually
6. go back and redo the entire HSA interview.
[Edited 3/11/2020 3:39 pm CDT - updated delete form instructions]
