F-7108 panel mounting angle

I'm installing an Affordable Panels panel in my rv7. I've almost got it all figured out, but I'm still confused about the mounting point for the F-7108 center rib. I've trimmed off the standard mounting point from the panel frame as described in the documentation. I had planned on following the procedure for using a small angle bracket to attach? the F-7108 to the panel frame. However once I got the ribs and the subpanel clecoed together the angle bracket as shown in their instructions is on the flange side of the F-7108. Is this just an error in the instructions or am I missing something? It seems to me that the angle needs to be attached to the other side of the rib. I'm confused. The other thing that is a little confusing is this is the same area where a platenut is supposed to be mounted. Is the platenut mounted to the back of the angle or is the angle just riveted onto the panel frame?

If anyone could help clear this up it would be very helpful. Any pics of this area would also be a great help.