what is the most # that aired on september 29, 2008?
CREATE TABLE "weekly_ratings" (
  "num" real,
  "episode" text,
  "air_date" text,
  "timeslot" text,
  "viewers" text,
  "weekly_rank_for_living" text
);
SELECT MAX("num") FROM "weekly_ratings" WHERE "air_date"='September 29, 2008';