A sum is been used to summarize the data of a field previously inserted in the report. Therefore, sum can only be defined for the fields added to the report.
Depending on the layout selected, the sums are displayed per group and/or at the end of the report, below each column.
By dragging and dropping or double-clicking, the fields from the field selection (data) on the left are added to the list of totals. The order of the sums can again be changed by dragging and dropping (in the browser version of the ad hoc report, the sum must be selected and moved using the arrow buttons at the top of the list). A sum can be removed from the list using the corresponding trash can icon.
By clicking the button, the sum operation is defined and - depending on the sum type - another field or a parameter. The available operations depend on the data type of the field.