When you select this button, you will see a list of all the global fields which may be affected by the template.
Those are fields with numeric masks (@n) and decimal places in them.
Among these fields, however, you may have several fields that you don't want to be touched, like for example "quantity" fields, that shouldn't be changed by the template.
You simply select those fields in this list, and they are not going to be touched by DigitChanger.