When scheduling activities and when these are in progress, there are three important values that must be read and analyzed for better understanding of project schedule. These three important values are displayed in Status Tab, as well as in the columns.  These important values are described below:

1. Original Duration:  This column or field shows the originally planned duration of activities, while these are planned. When we enter new activities in Primavera P6, we also enter their duration and that duration is called Original Duration. This value may be changed (if needed) before execution starts.

2. Remaining Duration:  This column/field shows duration of the activity yet to be completed. For example Original Duration of the activity was 10 days. Now, 5 day work is completed. So, the remaining duration for work is 5 days.

3. At Complete:  This column/field shows how much duration will have been completed when the activity will finish.Ideally, the duration you have planned for the activity should also be At Complete duration. This will be possible if the work is managed properly so as to complete it in the same duration which was planned.  However, this is not always the case and activity duration is prolonged due to slow work or non work, hence Original Duration doesn't remain valid in such a case, so we look at At Complete value to know in how many days the activity will complete with current pace. At Complete Duration is computed as Actual Duration+Remaining Duration.  The At Complete Duration can be viewed in the Status tab or in the column 'At Completion Duration'.