Summary Tasks and Percentage Required

[dushu]

I have set-up a schedule with many tasks and summary tasks with
resources and everything. While tracking the project I set the
percentages for the individual tasks - and microsoft project
automatically assigns the percentage complete to the summary tasks.
My
question is:

1) How does MSP calculate the percentage for the summary task -
Summary Tasks do not seem to show the percentage complete accurately.
The individual tasks all have the required percentage complete - but
the summary taks either shows delay (and in some cases ahead of
shedule) Please see screenshot at

http://www.ccaalumni.org/Summary.jpg

2) Where can I get a percentage required as per the baseline for each
task ?

Regards,
Dushyant Ahuja