C.s query

Hello friends i have a query about the following
 

I am a student of C.S. final. I want to know the rules regarding to set-off available to CS Final exams.

I have doubts in my mind. Suppose I applied for all 4 modules but failed in 2 modules(or remain absent in two modules) and passed in 2 modules then what will be the rules regarding set-off?  I am very confused for this.

For example take the following

 i secured the marks as follows

Module 1- 115

Module 2- 90

Module 3- 75(or remain absent)

Module 4- 90

then how will set -off be granted?

waiting for ur reply.

Thanks in advance