Select the Statistics tool from the Tool Menu of your site.
Select Reports from the Actions Menu.
Select Edit under the report to modify.
Modify report and save.
The options set when the report was created will be available to modify. Select Save Report to save changes once the edits are complete.
Note: Selecting Generate report will only generate the modified report once and will not save changes made to the report. Select Save report to save changes to the report for future use.