Complex sentence: The episode received a 8.4 rating in the key 18-49 demographic with 17.03 million total viewers, which made the show the most-watched series of the night, and earned it its second-best ratings.
Split into simpler sentences: The episode received a 8.4 rating in the 18-49 demographic range, with 17.03 million total viewers. It was the most-watched series of the night, with its second-best ratings.