What is the number of races that took place with points of 257?
CREATE TABLE "most_championship_points_in_a_season" (
  "driver" text,
  "points" real,
  "season" text,
  "races" real,
  "percentage_of_possible_points" text
);
SELECT SUM("races") FROM "most_championship_points_in_a_season" WHERE "points"=257;