How does apple trade-in work

Hi, I’m trading in my iPhone 12 Pro Max 128GB, I’ve gone through all the Get Ready section for iPhone 13 Pro Max 256GB version for tomorrow, buying the iPhone 13 in full with 1 time payment

how does the trade-in work if I get the phone delivered to the house? I traded in my iPhone 11 last year up at the apple store, trade-in was done instantly

thanks in advance