A fuel gauge is nothing more than a SUGGESTION of how much gas is in your bike. I IGNORE them.
+1
Ride by the odometer. Generally, you can trust the low fuel light, which will come on when you have about a gallon left. Seems that the stock gauge shows empty when you still have about 2 gallons left.
The 900 should be able to get better than 200 miles out of a full tank (filled to the bottom of the baffle on the sidestand), but obviously wind, weather, and traffic will impact MPG.
There really is a lot to be said for a petcock with a reserve setting. At that point, you KNOW how much you have left, rather than hoping that an electronic gizmo is correct. On my 1600, mine has been pretty consistent, but on ONE tank, for some reason the low fuel light came on when my gauge showed 1/2 tank. My mileage was also appropriate for 1/2 tank, so I ignored it. It hasn't done that since.