End date calculation into notification

Hi Experts,

I've a question regarding the "End date" calculation in notification basis the Notification Priority.

While i'm creating Maintenance notification w.r.t to priority " Immediate" system calculates say date X.

While same notification is being cretaed with priority type "Before next Mnt window" , system calculates say date Y.

How system is calculting these dates ?

Is during calculation, sysem takes care the workcenter capacity also for deriving the dates?

What is the config. setting for the same..?

Seeking your expert advise...thanks in advance..

Regards