Given a test case T that is included twice (two test executions E1 and E2) in the same campaign, all the charts (the "realtime" chart at the top of TestManagement, the chart in testplan, the donut chart in project milestones widget) will report that one test execution is not run (grey status), but it will not be visible in TestManagement, despite all filters.
Only the "latest" test execution E2 will be shown in TestManagement.
Technical information
Not sure how to reproduce this; it can be done by manipulating artifact links manually. Maybe by editing the campaign and removing / adding again the same test case T, it leads to two test executions E1 and E2, but normally E1 should no longer be linked to the campaign.