For Badaling Great Wall tickets, the definition of entry time of 7.30am - 12pm

Hi I am at the site to purchase the Badaling tickets and it states 2 types of entry times, 7.30am - 12pm or 12pm - 4pm. Does it refer to the time frame in which we can enter the Great Wall, or 7.30am - 12pm implies that we can only enter within this timing and exit the Great Wall by 12pm? Thanks