in fact, on some large aircraft such as Tristar, only one truck has luggage is present, it seems unreal - how should we proceed?
As explained on the GSX manual, and as discussed many times on the forum, the number of luggage wagons is calculated by GSX on the estimated number of passengers on board, obtained by adding the total weight of all loading stations, divided by 220 lbs. (industry standard to estimate weight of a passenger + luggage ), and it can change from a minimum of 1 to a maximum of 5.
Which means, if you see only 1 luggage cart behind the truck, it means you haven't loaded the airplane.