If you create a field in a form with additional features such as calculator, color picker, calendar etc. the control allows you to modify the field even if you disable it, and if you save the changes in the form the modified field is modified as well.
lets take a field of type double. and you enable the calculator for example. if you disable select the option “disable field: Update” and then run the form. you will find that when you modify the record the calculator is still available and you can modify the field and save the changes.
Regards