After reading the above, I believe I understand the difference between work and duration now. I am still having a problem, however. I hope someone can help.

Here is my example:

I have allowed myself two weeks (duration) to complete a task. In actuality, the amount of effort (work) that was exerted to complete the task was only 4 days. How do I reflect the 4 days of work as a task 100% complete?

When I populate 4 days into the "actual duration" column, it shows that the task is only 40% complete.

It would be helpful for the "duration" column to remain at 2w, to show the variance between estimated and actual time when performing the postmortem on this project.