Once you enter that you will withdraw all the excess contribution, the TurboTax interview figures that you are finished with the process and won't show it again - even if you want to see it.
This is one method that I know of to force that question to reappear.
Go through the HSA interview. When you get to the screen entitled "Let's enter your HSA contributions" (see screen shot below) and look at the second line:"Any contributions you personally made (not through your employer)"). Enter a number here like 1,000 (be sure to remember this amount).
This should force another round of "you have excess contributions", which should open the question that will allow you to change the withdrawal amount.
Note that the suggested withdrawal amounts will have changed since you added another $1,000 in excess contributions. That's OK; you are just trying to reopen that dialogue.
Once you have changed the withdrawal amount to what you wanted in the first place, now go back to the screen entitled "Let's enter your HSA contributions" and remove that $1,000 personal contribution that you added. Step through the HSA interview to make sure that everything is the way you want it.
