The low number is calculated from the minimum payload based on the length and number of berths plus the MIROA lot of new caravans can have MTPLM uprated to round number. What I don't understand is why advertise such lower odd number MTPLM to start with.
If low number is to increase number of cars that can tow caravan why odd number. Car tow ratings are typically round numbers eg 1200, not 1120kg.
Most buyers of new caravans are experienced towers and own car suitable for caravan size they are buying.