Thanks for your reply. I changed to what you say but still I have red where there should not be. Like here:
1st pack: 80 % (ok-green)
2nd pack: 100 % (ok-green)
3rd pack: 67 % (ok-red, he failed)
Course total: 82 % (not ok-it is green, but is should be red since the 3rd pack of exam is under 80%)
Is it a problem because there is no formula? Or because I have weighted mean of grades chosen?