First, this is completely wonderful tool.
I have a form where a user answers a question:
"Do you want one of these?" and if the answer is yes, it conditionally opens a few fields, include a product field with quantity disabled and a set price. This is added to the total automatically, as expected, wonderful.
If they decide a bit later that the answer is no, when they change their answer, the fields are hidden, but the price is not removed from their total until they either click "no" again or choose another product option. In other words, the total field isn't aware of the change until another price event takes place on the page.