what are the numbers of episodes that had 0.79 million US views?
CREATE TABLE "table1_28348757_6" (
  "no" real,
  "num" real,
  "title" text,
  "directed_by" text,
  "written_by" text,
  "original_air_date" text,
  "production_code" text,
  "u_s_viewers_million" text
);
SELECT "num" FROM "table1_28348757_6" WHERE "u_s_viewers_million"='0.79';