If I upgrade my Apple TV to Apple One, what happens to my Apple TV subscription?

See the following from Bundle Apple subscriptions with Apple One - Apple Support

If you already subscribe to Apple Music, Apple News+, Apple Arcade, or Apple TV+, you don't need to cancel those subscriptions. They will automatically be canceled when you're billed for Apple One.

But What about what they paid for already? For instance, I’m paid up on Apple TV until 2023. Do I just lose that or is it prorated in the bill?