Ball weight on two plates
The same push on the towbar shows up on two plates. When you add vehicle and van for GCM, do not add it a third time.
On the vehicle: GVM
Hooked up, the vehicle is carrying people, fuel, gear and the ball weight. GVM is that total. A van can fit the braked rating and still put the vehicle over GVM.
On the van: ATM
ATM is the whole van, including the kilograms on the towbar. GTM is the axles only: ATM minus ball weight.
On the pair: GCM
Unhitched vehicle plus ATM. That is the combination. The ball weight is already inside the van figure.
Braked rating
A 3.5 t braked rating is not a 3.5 t ATM van. The rating, GVM and GCM all have to fit.
Same kilograms, two plates. Two views of one load. GCM already has it once, inside the van, or inside a hitched vehicle figure.
We do not invent 10%. Missing ball weight stays Needs a look until you weigh the van or read a plate.