You should not need to manually change numbers on a form.
If you cannot answer the questions such that the figure appears where you think it should, you will have to contact Support.
Note that the online versions of TurboTax do not support Forms Mode.
All entries on Form 8606 in TurboTax come from other forms and information worksheets in TurboTax. Nothing is entered directly on TurboTax's 8606 form.
What line of Form 8606 do you think needs to change and why?