Hi Sir,

The Top 20 percentile is calculated by taking into account the marks of FIVE subjects-

• Physics
• Chemistry
• Mathematics
• Any Language, like English
• Any optional subject, like CSC or IP 

Now, the total is calculated out of 500 marks obtained in the FIVE subjects mentioned above and a list is prepared by your Respective Board, in your son's case "GSEB" and sent to JoSSA.

Keep in mind that it is necessary to be in the Top 20 percentile, only if you want admission in any IIT/NIT/IIIT/GFTI's, in other colleges, this criteria is not compulsory.

Therefore, if you want to take admission in any IIT/NIT/IIIT/GFTI's, it will not be possible if you are not in the Top 20 percentile.

You can definitely get other colleges.

Hope this helps you.

All the best!!!