I found the wiring diagram at Fulham's site. It is rather confusing ....
Fulham - Ballasts -
<I don't know if this link will work, but it is Diagram 11 for the workhorse 5.>
This is what I think:
The step 8 - You take the 2 red wires, join that to 1 wire that goes to the plug. You would want to do this with a wirenut. <Stripping the wire & joining at the middle is NOT to code ... mainly because the joint/insulation wrap may fail. To be totally to code, you would actually take the wires from the ballast to a junction box, do the joint inside, then run the wire out to the light. If you are mounting the ballast outside the canopy (best), you would also mount the junction box outside (use a plastic outdoor box, totally sealed once installed) & run the wires from the box to the light .... that way, the junction is not exposed to moisture.>
BTW - you join the 2 red wires to get proper watts. If you were running a 13W bulb (eg) you would only run ONE red wire to the socket. Joining the 2 reds together in parallel increases the juice going to the socket to power a higher W lamp.
Next you run the single wire (from step 8 ) & run that directly to the plug. You do not split that wire again to make 2. The diagram shows that you connect the two pins of the sockets with a jumper (this is step 1 - blue in my picture) & that may have confused you. There is a detail box in the link that shows this. To make this clear, I am attaching this drawing (I am only drawing one light, the other side is identical) :