What is the season # when ther are 5.3 million U.S viewers?
CREATE TABLE "table1_29102612_1" (
  "series_num" real,
  "season_num" real,
  "title" text,
  "directed_by" text,
  "written_by" text,
  "original_air_date" text,
  "prod_code" real,
  "u_s_viewers_millions" text
);
SELECT MAX("season_num") FROM "table1_29102612_1" WHERE "u_s_viewers_millions"='5.3';