Hello Dear,

You do not mention  exam in which you got 68 marks. But if you are talking about JEE mains then your percentile and rank  would be around 85.16 - 88.28 and 119896 - 170660

You can predict rank from the link given below

To more information about JEE Mains :-

JEE Main 2021 Exam - Answer Key (Released), Results, Paper Analysis, Question Papers (careers360.com)

Hope this information helps you...

Best of luck :)