It should say something about it in the manual...The site doesn't give out any 'extra' information, does it.
If you took a pic of what it looks like, maybe somebody would recognize it. I would assume it to be a 'finger type' 2-speed, and there should be an allen set screw accessable through a hole in the shroud or by removing the cover. Loosening or tightening this set screw will engage 2nd gear earlier or later. I believe that by turning the screw in, you engage 2nd gear sooner. I don't know for sure, as I don't have anything 2 speed.