How to set a default value

This is difficult to explain so apologies if it is hard to understand my question.

I have form values, when I don’t bind them to cookies they sets themselves to the default value I have specified with value=

The value is used in the form calculations, but when I bind that form field to a cookie, the value is replaced by the placeholder value and it is not used by the form in the calculation. That creates some problems for me for new users.

Is there a way to insert default (initial) cookie values so if a user comes to the form for the first time the form will have default values that work in the form calculations until the user overwrites them with their own entered values (which will become their cookie values)

Hope that was understandable - I would like the value to work just as it does w/o cookies if no cookies have been saved for a user.