Summary Usage Dialog Box
The Summary Usage box allows you to delete project summary usage data from the PSU table.
The Summary Usage dialog box displays a list of all the projects that have stored resource usage data for the open resource file. When you select a project from the list and click Delete, Open Plan frees the resources used by that project so that they can be made available to other projects.
You can select multiple projects by holding down the Ctrl or Shift key while making a selection.