The duration of a summary task is not necessarily the sum of the durations
of its subtasks. The duration of a summary is the time between when the
earliest starting subtask begins until the latest finishing subtask ends.
Imagine a summary with 5 subtasks with durations of 1, 2, 3, 4, and 5 days
respectively. These subtasks are not linked together in any way and all
start on the same day. The summary task's duration will be 5 days. OTOH,
if we link tham all in FS sequence the summary task duration will be
1+2+3+4+5 or 15 days. If some are linked and others are not, the duration
of the summary will lie somewhere between 5 and 15 days depending on the
links. You can even have a situation where there is a summary task that has
2 subtasks of 1 day each. The subtasks are linked FS with a 2 week lag time
between them. In that case the total of the subtask's durations is 2 days
but the summary task duration will be 12 days.
Hope this helps....
