After work begins on a task, you can quickly record its progress as a percentage .
When you enter a completion percentage greater than 0, Project sets the task’s actual start date to match its scheduled start date .Project then calculates the actual duration, the remaining duration, actual costs, and other values based on the percentage you enter .
For example, if you specify that a four-day task is 25 percent complete, Project calculates that it has had
one day of actual duration and three days of remaining duration .