At Completion Duration

At Completion Duration field

The total working time from the activity's current start date to the current finish date.

The current start date is the planned start date until the activity is started, and then it is the actual start date. The current finish date is the activity planned finish date while the activity is not started, the remaining finish date while the activity is in progress, and the actual finish date once the activity is completed. The total working time is calculated using the activity's calendar.