Hi @Debbie Smith‚
This most likely has to do with the timesheet settings that are set. Timesheets prepoulate and based on your settings in the Preferences page.
If the timesheet is populated before the task/issue/project is complete, it will show on the timesheet. Eventually, based on your timeframe in the section with the arrow in my screenshot, the completed items should drop off your timesheet.

I know this isn't the best solution since it doesn't delete it, but you can collapse the tasks/projects that are complete to help reduce your view.
