Based on my observation of my 05' X I consistently get 9.5 litres burnt before the reserve light and I tend to use at least another 3 before I fill up. On a couple of occasions I have seen 13.5 litres go in.
Based on my riding style and state of tune this kind of equals 190 km to reserve and 260 km before I want to fill up even allowing for a half litre of unburnable fuel at the bottom I think my bike would do 300 km if by my poor planning I had not filled up earlier.

A word on the reserve light.
When you are past 8 or 9 litres (or so) used and going up or down an incline for a period it can cause the sensor to trigger the reserve light, if you then hit the flat and the light goes out and you then run 5 km with out triggering the sensor again your F-TRIP on the dash will reset.
Likewise if you filled up and did not clear the F-TRIP as you ride down the road it will reset and revert to odometer after 5 km.

Regards
Marcus