By default, data tables include a Column Totals row, which consists of a row of values with sum totals for each column. Optionally, you can enable a Row Totals column, which consists of a column of values containing sum totals for each row.
The following image shows a detail from a data table with row and column totals enabled and added text indicating which is which:
To toggle the totals on and off:
Navigate to the Customization tab in the Chart Builder.
In the General Customization section, set the Column Totals and Row Totals toggles to the desired settings.
For a complete list of Chart Customization options, see Customize Charts.