What is the highest play-offs that have stevenage borough as the club, and a total greater than 21?
CREATE TABLE "topscorers" (
  "player" text,
  "club" text,
  "league" real,
  "play_offs" real,
  "fa_cup" real,
  "fa_trophy" real,
  "total" real
);
SELECT MAX("play_offs") FROM "topscorers" WHERE "club"='stevenage borough' AND "total">21;