they go by size and weight and they have a scientific formula where they measure the girth and lenght at various predetermined areas on the antles to come up with a score, that is recorded in boone and crockitt or pope and young.they are very good eating it is a red meat and is not very gamey. my brother who lives in new mexico got a gamesbok last year on a special hunt i will try to post a pic, it was only about 350 lbs with 22 inch horns he said it was a little one ??