Just like in this screen shot.
Most Helpful Girl
the MHO is the average of most help full of total opinions.
if you open each profile you'll see the guy 4 Xper may have answered 5 question and he got 3 of them MHO so his percentage is 51%! and the other guy has answered 500 questions and only 50 of them got MHO and thats why he's 8%1