Name the number of number in series for production code of 06-04-621
CREATE TABLE "table1_1876825_7" (
  "no_in_series" real,
  "no_in_season" real,
  "title" text,
  "directed_by" text,
  "written_by" text,
  "original_air_date" text,
  "production_code" text
);
SELECT COUNT("no_in_series") FROM "table1_1876825_7" WHERE "production_code"='06-04-621';