Answer:
The Dursleys didn't like magic and already knew it was real because aunt petunia sister/Harry's mother was a witch and went to Hogwarts. Harry didn't know magic was even real and that Hogwarts existed because they hid it from him. He only thought that maybe magic was real because he opened the snakes cage at the zoo and he understood the snakes words.
Step-by-step explanation:
Sorry if it's wrong, I think it should count though because I read the book and watched the movie