If that's the manufacturer's recommended max weight, then that's it.
If you're looking for a "max weight" you could carry, then start loading it up. If you go too far, then its a bit less than that.
Also be aware static load maximums are always higher than dynamic loads. Just cos you can stack hundreds of kilograms on doesn't mean the bike will handle that while moving, and braking becomes quite sketchy when parameters are exceeded.
However, a real world example. I have a small kid's trailer, which is rated to 35 pounds or 18 kilograms of live load. I have carried two lead-acid UPSs, and weighed the whole trailer at 100 kilos when I got home.
The bike was hideous to ride - I was towing the trailer with my 20" folding bike, even at 15 gear inches it was an effort to get over any grades. And these grades were merely "crossing the crest of a road" at an intersection. At one point I had to ride up a half-metre high railway crossing, and it was horrible. Then, going down the other side was like a runaway rollercoaster. I also managed to barely avoid jackknifing the combination when stopping for a red light.
And for my efforts, I managed to subtly bend one of the stub axles on the trailer.
Upshot - the manufacturers recommended limits are what they set. While you can probably exceed them, all the risks and consequences are on you. I would not expect a warranty to be serviced if you routinely overload the bike.