In Figure 14, you can see the power supply label containing all the power specs.
As you can see, the label says this unit has two +12 V rails, but this do not correspond to the reality. Inside the power supply all +12 V (yellow) wires are connected to the same place and the monitoring circuit doesn’t support over current protection (OCP), which is a prerequisite to have more than one virtual rail. Therefore, this power supply has a single-rail design. The manufacturer lists OCP as a feature from this unit on the text present on their website, but not on the feature list available on the same page, so they probably just copied and pasted the text without paying attention (just to clarify, this unit doesn’t have OCP).
On the manufacturer website it says that this unit is based on a single-rail design. So the label is definitely wrong.
Now let’s see if this power supply can really deliver 520 W.