Than why you say me that your marks is268 ,why you lying  us.  If you don't know the  format  of finding marks  simply say no  ,why you saying that I was gain 298 /360 . That's unfair  .sorry if  something  pinch you  .but  that's really unfair.  I am very upset  with your service  , ....

As per my higher authorities we can't convert percentile into marks in JEE exam. 

This percentile means you are better than 82 members who wrote the exam.

Your question is incomplete 

Out of what have u got this percentage?