You can use group functions when you have grouped the data, and you want to see the group totals, for example. If you right-click a column on a list form in Isah (List tab), you will see the group functions: Total, Maximum, Minimum, Average and Quantity.
To apply a group function to a group of lines, right-click the column header by which you have grouped the data. Choose Group functions and then the option you want to use. You can see the result of the group function at the bottom of the group.
The group functions are saved of a per-form and a per-user basis, so you do not have to reset the group functions the next time you open the form.