Yes, there are two positions. The difference is the amount of fuel where the light comes on. The problem is that it apparently is not a trivial operation - not rocket science, but it isn't a five minute operation. IIRC the lower position is something like half a gallon, the upper position more than a gallon?
When I had my 70 deg. tank fitted I had the sensor fitted too (my '09 didn't come with it) and I had fitted in the lower position because I figured between the two tanks that there would be more than half a gallon at that level - probably closer to one gallon. When I first rode it afterwards the light did come on when I was on the trail - I rode 12 miles to the nearest fuel and filled up and it still had at least another half gallon left in it (I don't know if that was usable - I have to do some experiments to see how much is usable now) so I think I figured about right.
