In order to get a higher voltage rating they are saying to put breakers in series.
For a switch rating of 440V DC or 550V DC you can put the + and negative in one side and the load on the other side.
Since the first picture set shows the load on both sides, we know the breaker is not sensitive to polarity.
You can use the two-pole switch to get a 800V DC rating by putting the two breakers in a series.
However, in this configuration, you are only switching one leg. What is happening here is that there are now two places where the circuit opens. This effectively doubles the contact gap, giving the switch a higher ability to snuff any arc that forms. Notice, however, that the voltage does not double. Clearly, the physics of the voltage snubbing in the breaker has more factors than just the size of the contact gap.
Note: The company probably sells a tabbed busbar/Jumper that fits into the two connectors on one side so you don't have to use a piece of wire for the series connection... the breaker may even come with it.)
To get an even higher voltage rating, you can use a 4-pole ganged breaker. The bottom series of pictures shows various arrangments to accomplish up to a 1200V rating.
Notice that in some of the diagrams, all of the breakers are on one leg but in other diagrams, only one or two of the breakers are on one of the legs. The first time I saw this, it confused me but then I realized it did not really matter where in the circuit the break is. The total gap and whatever arc Snubbing they have is still part of the total circuit. Therefore, you can wire it with two on each side if the application requires a switch on both legs.
Does this mean that only the negative cable connects to the load or am I missing something? Any help is appreciated. In the manual it shows several wiring options but the one I have is 800vdc so I assume only those two options will be correct.
Do you have a 2 gang or 4 Gang version of the breaker? What voltage rating does your circuit need?
If you have the 2 gang and you need the 800V rating then yes, the power negative should go to the load and the power positive should go through both breakers.
If you are using this for a PV disconnect and need the 800V, then the 4-Ganged version is needed.