Most Helpful Guy
Notice where the ribs end. That "eighth pack" is the rib cage.
^above do you see, The upper most part is a rib.
In my opinion (witch is highly valued by many) It is not considered another row of abdominal muscle, Its your f***ing rib cage.
Anyway, I never found abdominal muscles all that illusive, I've had them naturally since I was a teenager.