Percent Complete Conflict in Summary

In the P6 Projects Overview screen, the "Duration % of Original" value for my project is about 18%. I also performed the following calculation in excel by exporting the duration columns: (Planning Duration-Remaining Duration)/Planned Duration *100. The value here is only 3%.

Why is the summary % value different from the conventional formula - are both these not measuring the same?

 

The default Percent Complete Type is set to 'Duration' for all activities as well.

Thanks,

Kashyap