Well each subject is assigned a specific number of credits. Then there is a grade assigned against that subject.The grades assigned has specific values.They are O-10,E-9,A-8,B-7,C-6,D-5,F-2,I-2.Now each grade u get on a subject is multiplied by its value with the number of credits for that subject.Then to calculate the Grade Points Awarded , the sum of the products is divides by total number of credits.For example there are two subjects with credits 3 and 2 respectively and u have got O and E respectively.Then your GPA is =((3*10)+(2*9))/(3+2)=9.6.