When do I use a single parentheses and when a double one in the Form Calculation

Please explain, when do I use a single parentheses and when a double one in the form calculation widget.

I recommend reviewing also our user guide on: How-to-perform-calculation-in-the-form

The Calculation formula editor is just like any normal calculation creator.

The formula should be enclosed on parenthesis if there are nested calculation being done. 

Ex:

((1+2) * (3/4))

As you can see on the example this is a nested calculation. So the formula needs to be contained on parenthesis as needed.

Hope this help. Let us know how we can be of further assistance.