Complex sentence: At first, the final round consisted of 30 seconds of $15 questions; later, this was replaced with five $20 questions (called "The Century Round," as the total value of the questions was $100).
Split into simpler sentences: At first, the final round consisted of 30 seconds of $15 questions. Later, this was replaced with five $20 questions (called "The Century Round", as the total value of the questions was $100).