How many of the episodes in the top 50 rankings were originally aired on June 28, 2010?
CREATE TABLE "new_zealand_tv2" (
  "episode_number" real,
  "title" text,
  "original_airing" text,
  "timeslot" text,
  "viewers" real,
  "top_50_ranking" real,
  "scripted_show_ranking" real
);
SELECT COUNT("top_50_ranking") FROM "new_zealand_tv2" WHERE "original_airing"='June 28, 2010';