The points one receives/loses depend on who is giving the rep. Different people have different rep power. The more rep they have, the more points they give when they rep you. Or at least that's how I understood this thing. :lol:
when you rep someone their rep goes up depending on how much rep you have, when someone reps you your rep goes up depending on what their rep level is. The top reputations are a 30 day stat and it shows how much rep someone has recieved in the past 30 days.