bit strange there are no letters etc. you usually have the unladen weight, the max laden weight, and the then the front and rear axle weights, but non of those figures add together to correspond. some one else might come along and explain. edit....and they have done.
The two explanations are spot on and no they will not add up, the 3850 is a weight with everything and everyone in that you cannot legaly exceed, again fully loaded your rear axle must not exceed 2120Kg and similarly fully loaded your front axle may not exceed 1850 Kg the other figure is your maximum allowed weight with a trailer hooked up
Sometimes best to get the van weighed as you would normally run it, then make adjustments. My local trading standards will weigh the van for free, they only charge if you want the printouts and certificates. You can use the loaded weight to get tyre pressures from your tyre manufacturer. As stated above, better to be safe.