How many directors directed an episode that reached 2.48 million viewers?
CREATE TABLE "table1_27047554_1" (
  "no_in_series" real,
  "title" text,
  "directed_by" text,
  "written_by" text,
  "original_air_date" text,
  "u_s_viewers_in_millions" text
);
SELECT COUNT("directed_by") FROM "table1_27047554_1" WHERE "u_s_viewers_in_millions"='2.48';