Hi supan,
I think you may safely ignore that section - the supply nets seem to assign to the plane automatically based on your Xpedition plane assignments. If you use Viewing Filter (RMB > Show Viewing Filter) and hide everything except that supply net, you should see the traces, vias, and pins all tied to that plane. Hovering your mouse over the plane shape, you'll see in the bottom-left it should have the correct net name assigned.