Total Duration Rollup Issue

[davesaint]

First of all I'm not even close to being an expert using MS Project so I hope my questions are easy for.

A co-worker of mine developed a 300 line item schedule using MS Project (2000). He asked me to take a look at it because his total project time span was 8 months but the roll-up of the project duration was 668d?. I looked at the outling (summary tasks/children) and everything looks fine. What's going on here most likely? What do the question marks mean after each duration?

 

[PDQBach]

Question marks indicate that the duration is an estimate not directly entered by the user.

Why should durations in sub tasks total up to the project duration? That doesn't make sense. Assume a project with two parallel tasks each lasting 10 days. The duration of the project is 10 days; the total of the durations of the tasks is 20 days.

Look up the difference between Work and Duration.

 

[davesaint]

If had your project calendar set at a 5-day work weeky and had two weeks of work that is 10-days correct? If you have 10 tasks in the schedule with varying task durations with the earliest task starting on day 1 and the latest task finishing on day 10 wouldn't the roll-up of line one equal 10 days total as long as the outling is correct?

 

[PDQBach]

For a task:
Duration = the calculated number of days between the start date and finish date of the task. (Note, if you change the number of days of duration then Project will adjust the Start or Finish dates as necessary to reflect the number of days that was entered in duration.)
Work = the number of days of work necessary for the task.

For a summary:
Duration = the calculated number of days between the earliest start date of the sub-tasks and the latest start date of the sub-tasks.
Work = the sum of the work days of the sub-tasks.

(An adjustment of my earlier answer: the question marks in duration indicate that this is an estimate. You can enter a number to show that this is your estimate or you can enter a number and a question mark to indicate that this is a preliminary estimate.)