This array contains names of fields for which given field has to be calculated in totals. If the array is empty, total is calculated for all fields.
You can specify the Hierarchy keyword after field name and a space. Adding this keyword means that expression will be used for hierarchical group by field, specified before the word, and all nested groups, for which their own expression of the given resource is not specified.
If the array is empty, totals will be calculated for all fields.
Can contain the Overall string to specify the necessity to calculate in the overalls.