Two notes: 1: The RU setting is the MAME default (difficulty 1/Easy), so all of your RU scores need to be integrated into the Easy list and removed from Medium. 2: Chrispy on RU is me. But since I beat that score anyway last night with my MARP score, the point is moot.
(EDIT: looks like Jry beat me to the punch by a few minutes!)
Something worth considering: for the purposes of this forum, it might be better to refer to the levels as "difficulty 1,2,3,4", rather than "Easy, Medium, Hard, Hardest". Those are MAME-specific designations.
The arcade manual, which, IMO, should take precedence, lists the four levels as "Easy (1), (2), (3), and Hard (4)."
Sticking with numbers is a compromise between the two I think, but more importantly, would eliminate the confusion around which of the settings is meant when people say "Medium" or "Hard." The numerical difficulty is unambiguous, and going by number will always make clear which one is meant.