[Koha] Circulation module of Koha

[Library]

hello everybody,
? in circulation section why we need to decide the return date (Sticky 
Due date),i think this may be the automatic function &
THE MAIN PROBLEM is:
it accept the more days than the defined days in the categories.
For example : if we provide  the issue service to  the students for 
2weeks, & here in circulation module if we issue the book even for one 
year it accept although only 2weeks permissions set for the student 
category in Borrower categories.
Why?
there should be a link between the  Borrower categories & circulation 
module's due date..


-- 
Kanwal
Guru Nanak Dev Engineering College
Ludhiana (Punjab) India