These two fields are not related. Qty. on Job Order represents sum of this item quantity on all Job Planning Lines. This is planned consumption quantity for jobs.
Qty. on Component Lines shows quantity of the item that are needed for Production Orders. The same quantity cannot be on Job Planning Line and Production Orders Components in the same time.
Qty. on Prod. Order shows quantiy of the item that have been planned for production and this is not related with consumption on the Job Planning Lines.
You can see this demand flowchart on my blog (I am still not finished): community.dynamics.com/.../inventory-planning-part-2.aspx