It should be pretty reasonable to ask for the mileage on the odometer on delivery you’d think?
Surely this would be recorded by the delivery driver as a backup to the dash cam (or so you’d assume).
Otherwise you’ve got to either use the trip meter (probably not the best if it is used for actual trips or range recording) or jot it down in your phone’s notes app- it’s not a number that changes and it’s also easy to do the calculations (1,000 a month) by looking at the odometer?
Given the prices of the mileage addons, and the likely impact to the end of ownership price (that Onto will recover on selling the car) I’d be very surprised if unlimited were offered. It’d be pretty easy to abuse and coupled with free charging would cost too much to maintain I would think.