I have some questions about the first contract in Korea!

Hello! I'm a foreigner who has recently arrived in Korea. I just received my first contract and have a couple of questions. First, I'm curious about the vacation clause. It says, "The employer allocates paid leave according to the school schedule, and the remaining days can be used by the employee." Does this mean I can't freely use the 11 days of vacation I receive in my first year? I have to attend my younger sibling's wedding in March next year, but the date hasn't been set yet. Second, it's about the starting date of employment. It says, "The employee will start work 1-4 days after arriving in Korea, and the first 1-4 days will be considered unpaid leave to provide adjustment time." I want to start adapting as soon as my visa is issued, but I'm far from Seoul or Busan airports and would like to spend a few days in Seoul. Does this mean I can't start earlier than 4 days before my official start date? Will this period be considered as vacation? I would really appreciate your help in understanding this!