Time calculation in work center- Dynamics NAV Manufacturing

Ashoka-NAV

Hi All,
My client use NAV2009 R2 W1+ Manufacturing;
This is the scenario;
Work center B has assigned to production item A.
Work center B;
It is a oven.It can hold 1000 items at a time.Its holding time will vary item to item.
its 2 hours for item A.
now i have 3 production orders. each 120 of item A, 200 of Item A and 300 of item A regularly.
Whole quantity of item A(620) work center run time is 2 hours. (Qty 1 to 1000 its 2 hours).
how can i set the time in route card?
I need to set the time to calculate accurate time at the planning worksheet.
your comments are highly appreciate.:)