Work center effect on Work Duration in Activity

Hi,

I am involved in PM but got to investigate the effect of Calculation key in Work center on Project activities.

I have a workcenter with following details:

1. A work center (e.g Proj) Work center category 006.

2. Capacities tab with category (eg. Labour)
     Other formula  :SAP008
     Inside the capacity: calender ID, base unit of measure as HR.  I also mentioned the start and finish time for the work center (e.g 0730 hrs to 1700 hrs),
     gave break duration (e.g 1 hr, 30 min ) capacity utilization 80%, 04 number of the capacities in that work center..

3. In scheduling tab: other formula (SAP004)

Now i created a project with activity. I gave the Work center as "Proj" (defined above) with other details like WBS element etc

I selected the calculation key as "01 Calculate Duration", gave the Work as 10 Hrs. Upon pressing enter, the capacity fills up with 1 and Percent with 100 and it shows the Duration as 10hrs.

My query: Whats the effect of Work Center where i set the no. of capacity as 4 and Cap Utilization as 80%. There seems to be no link between the work center provided and the calculation.

Please assist!

Thanks