Use of Differnt Calenders P6

Hi All,

I wonder if you can help using p6.7, have put together schedule but have used two different calenders within the schedule. One calender a Ten day fortnight 9 hr working time the other 7 day calender working 12 hr days.

 

On the activities using 7 day calender if I put a duration 0f say 19 days for an activity the start and finish dates show a duration of 13 days. I have checked correct calender assigned to correct activity but it still comes out with the same result!

 

Can anyone throw some light on why this is happening Cheers!