hey,

to calculate four subjects percentage , you need to keep following things in the mind otherwise you may face deduction in your aggregate

1. you need to include one language subject (core/elective/functional)

2. one subject in which you are taking admission let say you are seeking admission in B.A history hons then you need to include history subject in your best four otherwise it may lead to deduction of 2.5 percent and if you are from science stream and taking admission in any of the arts course then it may also lead to a deduction of 2.5 percent.

3. rest two of the subjects you may include from the list A having (i will attach the link) , if you may not then it will also lead deduction of some percent.

for more information kindly go through the link mentioned below

https://university.careers360.com/articles/delhi-university-admissions-how-calculate-best-of-four-marks

good luck!