Cannot clear data out of Discovery Dashboard even when incidents are set to ignored

Try deleting the incidents rather than ignoring them. Select Main > Discovery > Incidents.

To delete a single incident, locate the incident in question and click the box on the far-left side. Locate the red X in the tool bar. Click it and select Delete Selected Incidents.

To delete multiple incidents, use the display and column filters as appropriate so that only the incidents you desire to delete are displayed. Select all displayed incidents.

Click the red X in the tool bar and select Delete Selected Incidents.

This should clear the incidents from the dashboard summary.