To change the type of summary for a specific column or apply a summary, do the following:
Right-click a region within a group footer or grid footer under a specific column. A context menu displaying a list of supported summary types will be displayed.
Select the required option from the context menu.
To calculate summaries against all nodes, ensure that the All Nodes menu check item is checked. To calculate summaries against root nodes only, uncheck the All Nodes check item.