I got to experience the Low Fuel light in the 980 the other day, a first for me. As I mentioned in another thread, I've had some difficulty in getting full fuel, although it comes close. The other day, I was returning home and the weather was clear, lots of alternates around, and it seemed like the perfect time to stretch the fuel a bit and see how she behaves.
I planned to arrive with around 500 pounds, and about 10-15 miles out, the Low Fuel light came on, which indicates 150 pounds or less on one side. The procedure for Low Fuel light is to turn on the Low Fuel pumps, which scavenge fuel from the outer bladders into the feeder.
The thing to know about the Low Fuel pumps is that, once you turn them on, the Low Fuel light may go out (it only flickered in my case), and the indicated fuel quantity will increase. Of course, this doesn't mean you actually have more fuel, just that it looks like you have more fuel.
When I shut down, the fuel gauges showed 300 pounds on one side, and 200 pounds on the other. However, I think that's more than I actually had due to the indication issue I mentioned above.
The other thing to know about fuel in a turboprop is that you really don't use all that much less in the descent than you do at cruise at altitude, and certainly any savings you might realize are more than used up during any low altitude maneuvering. So don't count on burning less as you start down.