How does apple pay charge your card, if they don't store your card number?

If this post is not allowed, would you just give a warning? I'll delete it.

Apple claims your card number is not stored on your device, nor is it stored on apple servers, if this is the case how do they charge your card when you make a purchase? They must be keeping your information somewhere, where do they store your info?

*"When you make a purchase, Apple Pay uses a device-specific number and unique transaction code. So* ***your card …

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