You've earned a day in the chamber of fire

Jan: Mom, Dad, I found cigarettes in Greg's jacket.
Dad: Greg, were you smoking cigarettes? - No, Dad.
Dad: He's lying. There's no doubt about that. Greg, I'm afraid your punishment will be four hours in the snake pit. That'll give you time to think about what you did.
Jan: Man! That'll teach him.
Dad: Jan, I'm afraid you've earned a day in the chamber of fire for tattling on your brother smoking.

I am wondering why Dad used present perfect instead of will in the way he used in the underlined part when he wanted to punish his son! Her father has not yet started the punishment why did he use present perfect?

Here is the clip: