Got it from my travel agency. They contacted Latam Airlines to get those information.

Yes, I can agree with you. For example if on the list are 6 people and there's 6 available seats in business class then all 6 people will get the upgrade. Unless, if for example some flight will be rescheduled, and latam will have to move some passengers from business class to other flight (your flight) then you might lose your upgrade. But that never happened to me so I'm not sure.