Thanks for patiently waiting! It was indeed $1000 off. Here's how promotion works. The trade-in value of your iPhone 12 Pro which amounts to $220 will be credited to your bill. While the remaining $780 will be divided into 24 months and will apply as your monthly credit

The original charges for iPhone 15 Pro Max is $50 but since you have monthly credit of $32.50 ($780/24mos) you are only being billed for $17.50. Kindly let me know if you have any clarifications about this. I'd be more than happy to assist you further :)