3 pieces are still open. The task completes on its own once the last one is signed off.
There is no button here to mark this done. A task completes when the work beneath it is signed off, so the state always reflects what has actually happened rather than what someone declared.
At most 4 people hold pieces of one task. Small groups finish things; large ones negotiate. The maintainer is not one of those places — they set the task up and sign off.