Calculation Field allows you to perform a series of arithmetic computations to a set or a series of fields.
The example below shows how you can sum up the amount field using the Form Grid.
Figure 1: Configuring and Obtaining the Field ID from a Form Grid
In the Calculation Field configuration, add a new variable that will map it to the field set in the Form Grid earlier. Match the From Grid's ID and field ID in the variable field ID, as shown below.
Figure 2: Configuring the Calculation Field
Figure 3: Calculation Field in Action
Using JavaScript Math Object in Equation
The "Equation" setting of Calculation Field is supporting Javascript Math Object. For example, to find the max number among several fields in a form, you can use Math.max() in the "Equation". 