There are two rate by options "Top Movies" and "Strictly by rating".
"Top movies" take into account the number of votes and use the same algorithm as IMDB does for their top 250.
"Strictly by rating" does what it says. It sorts movies strictly by rating, and only includes movies that have at least ~8 reviews on RT, ~25000 on IMDB.
To be more clear, I suggest that Strictly by Rating require a minimum number of user reviews counted, and excludes movies with RT Audience reviews still in a "Want to See" status.
"Top movies" take into account the number of votes and use the same algorithm as IMDB does for their top 250.
"Strictly by rating" does what it says. It sorts movies strictly by rating, and only includes movies that have at least ~8 reviews on RT, ~25000 on IMDB.