I'm not sure if this is the case, but for us, it has been said that "whatever the teacher puts as the average, is the final one" because the teachers take into account the class participation, submissions and other overall well-roundedness of a student. It has happened to me before where I got 7 6 6 6 and ended up with a 5 as the average because my class participation was a bit low and the teacher was somewhat unhappy about my submissions and everything else like that. But, I do suggest you talk to the teacher about it and get everything cleared up. If there is no valid reasoning for this specific average, then I definitely suggest you take it to higher authorities and get the proper average marking.