You can edit custom and default reports to suit your needs.
Go to Reports.
Click
besides the report you want to edit.
Make necessary changes and click Run Report.
A new report is generated with the modified data.
To save the changes to the original custom report, click Save on the toolbar. You can click Save report as to save the changes as a new report.
While editing default reports, you cannot save the changes to the original report. Instead, you can use Save report as to save the edited report as a new report.