1. The prefix "수" is used to indicate "amount" where you don't know exactly but you think there are a lot or some. dozens of pages = 수 십페이지 hundreds of pages = 수 백페이지 thousands of pages = 수 천페이지 2."나" is used to emphasize that there are a lot than you expected, so that you are surprised a bit. 3.The dictionary form is "되다" not "됩다". 되다/됩니다(formal, polite)/되요(informal, polite)/되(informal, not polite) It literally means "to be/become", but it is used to mean "to have/contain/cover" here. \^o^/