see 10 doesnt exactly mean 92.5%.it means >=92.5% a stupid calculation is there!!! you see there are credit scores for each subject(check wbut syllbs).suppose you get >90 in physics.then they will take 10(highest score) and multiply it with the credit (e.g.-4 say).next in chem say you got >80.and let the credit score 3 for chem.then its 9 X 3.for any subject >70 they take 8 for >60 7 and so on and add it all together.here total for physics and chem = 10*4 + 9*3 = 67 after that sum of all products you got to divide the result with the sum of credit.here its 4 for physics and 3 for chem.so total = 4+3 =7 so your score in wbut is 67/7=9.57. now you see we are considering full points i.e 10 for every subject where we are getting >90.so its not for 100 in theory we are getting 10 but for >90. hence they doesnot give the actual percentage.i.e here 9.57 is not 95.7 %.so according to AICTE the standard deduction is (grade - 7.5) *100 %.that way you will get your approx percetage.!!! hope you got it!!!