How to Maintain Priority Duration for business transaction(T-Code : notif_create)

Hi!! All,

Can any body guide me how to maintain priority duration for a business transaction .

I am creating a ticket using t_code : NOTIF_CREATE and

system is automatically assigning 3 days for all priorities.

I want to assign  4 days to low priority

                         3 days for medium

                         2 days for high

                         1 day for very high

Thanks in Advance

Akshat