Why are backlog items with status "Done" shown when selecting "Items not yet completed"?

There are several possible reasons for this:

• A backlog item in a sprint is not considered "completed" until its sprint has also been completed.
• A backlog item in a Kanban board is not considered "completed" until it has been archived in the board.
• A backlog item of type bug is not considered "completed" until it has been closed.
• A backlog item inside an epic is always shown, regardless of its status, until the entire epic is considered "completed".
• An epic is not considered "completed" until all of its child backlog items are considered "completed".

To leave out the backlog items with status "Done", you can select "Filtered items" instead, and create a filter with a Status criterion that shows the statuses that you want to see. Click "Hide other items" to hide the backlog items that don't match, instead of just graying them.