Percentage is calculated based on top 5 scoring subjects . If you have chosen 6 subjects then first of all you have to pass all the subjects . Second , your 1st subject is fixed that is language subject . It may be english , hindi or any other language . Now your top scoring marks in 4 out of 5 subjects will be selected . You have scored good in music compared to physical education . So your music subject will be added . It means you will get 70% in your result .

I hope this answer clarified your doubts . For further any doubts , feel free to comment .