Engagement Numbers Are Different For My Post

Hi if I am posting something and then boasting it, I often get notification that it is liked by 1000 people but when I go to the actual page, it shows, it is only liked by 200 people. Why there is that difference and how can I show all the 1000 likes on my page, I want people to see that it is liked by 1000 people when they visit my facebook page.