5. This sentence is about a car park manager's plan for charging different rates for different floors:
さっそく2階は1時間200円にして、3階はそれより さらに50円安くしました。
I understand this OK apart from さらに. The dictionary definitions are "furthermore; again; after all; more and more; moreover; even more", which seems almost the exact opposite of the required meaning, given (I assume) that the third floor is 50円 cheaper than the second?