Hi greetings

Yes you are correct the difficulty level of overall question paper may be different for different shapes of the chairman therefore to balance this problem the normalisation will be done for separate shifts suppose you appear for the exam in 1 shift then your percentile score will be calculated based on the o students of your shift not with the others and therefore there is nothing to do with the absolute marks because the percentile score will tell you the position of you with respect to others to avoid any kind of discrepancy the percentile will be calculated upto 7 decimal point.

Hope this helps all the best