Hi, admission to DU is based on your marks in best 4 subjects and not overall percentage in the qualifying examination. There some important instructions that you should know while calculating best of four percentage for Delhi University:

•  You need to include one compulsory language(core/elective/functional)
•  Your second subject should the one in which you wish to seek admission. If you don't include that subject then   2.5% marks will be deducted from your best of four percentage
•  The next two subjects should be academic/elective subjects according to List A. If you don't include subjects as   per List A then 2.5% marks will be deducted from your best of four percentage.

So if we include all the subjects in your best of four calculation according to the rule/guideline there shouldn't be any deduction.

In order to see the subjects included in the List A and for further information regarding best of four  check the link below.

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

Good Luck