I've never seen anything like this, and my friend just got this carb with his latest engine.
I think I got a picture to come through with this post, but if it fails for some reason I'll repost the picture in the comments.
Perhaps the second cable is for holding down the float for some extra gas to start the engine. I would suggest a choke cable since I'm not seeing a lever. So what is it?
Since a choke... welll... chokes performance, some companies use mixture enrichment jets instead of a simple choke. Not sure why anyone needs performance on a cold engine anyway, but it does work.