What does this mean?

Tire pressures can be confusing - Think of them this way. You want the pressure in the tire that will keep the tread in good contact with the road. Too low pressure the middle of the tire does not press hard against the road. Too high a pressure the middle presses real hard but the edges don't. The right pressure, the tire edges and middle all equally share the weight. Now the tricky part is, the right pressure depends upon how much weight you're asking the tire to carry. The more the weight, the more the pressure is needed to keep the tread flat on the pavement. This works great - until you get to just too much pressure in which case the tire would rupture. Fortunately, every tire manufacturer I know gives you a weight chart. You get your axle weight measured at a truck stop, say it is 12,000 pounds. Ideally you measure both sides and each should be close to about 6,000 pounds. Take the max weight (6,000) and divide it by the number of tires on that side (in my case, 2 tires on the right and two on the left). So I now each tire needs to support 3,000 pounds of weight. Then I look on the chart and see that I need to inflate to 80psi. And, that is just what I do. The tire chart also says max inflation is 110psi but I'm well below that limit.

So your Sendel tire, if inflated to 100psi, would be flat on the pavement if it was supporting 3,850 pounds. If you're loading it with less weight, less PSI is needed.

Does that help?