
What affects the % completion is not duration, but actual effort. Duration should have no impact at all on % completion. If you have a task with let's say 10h of work (estimated work), and you report 1h of actual effort, the % completion will automatically calculated to be 10%. If you put 0 in remaining effort, it will automatically mark the task as complete and set the % completion to 100%. So either you report progress via % or effort. Hope this helps!