One grade, three ways to say it: a C-code, an A/B/C letter, and the Nigerian term you already use — and a colour that confirms it at a glance (green is best, red is parts). Cosmetic grade is how it looks; functional grade is whether it works. We grade both. The grade is the promise.
The cosmetic grade describes appearance only. Each row is one grade: its C-code, the A/B/C letter, the Nigerian terms sellers use, what it means, and what it looks like.
A separate axis from looks. A laptop can look clean (C6) but have a major fault (F2) inside — so we always state both.