There's multiple factors at play. First is no, it's not an average of the 4. They are weighed differently, don't remember off hand which are higher and lower. Another is if 2 sub grades are the same, the lowest one will be the final grade. So say you have a 9 - 9 - 2 - 2, the final grade WILL be 2, regardless of the 9s. Last I can remember is the highest final grade can only be 1 point higher than it's lowest grade. So if you have a 1 - 9 - 9 - 9, this card will have a final grade of 2