Table schema:
CREATE TABLE table_27319183_7 (official_itv_rating__millions_ VARCHAR, total_itv_viewers__millions_ VARCHAR)

Question: What were the official itv ratings in millions for the episode with a total of 8.53 million itv viewers
SQL: SELECT official_itv_rating__millions_ FROM table_27319183_7 WHERE total_itv_viewers__millions_ = "8.53"