danath, you can adjust your float to make your gauge register however you like. You can have the gauge show empty when there is still a half tank if you like. If you want your gauge to be accurate showing full when it's full and empty when it's empty, the method I recommended works well.
No matter how your gauge reads, your fuel light will not be affected. The blinking fuel light is actuated by a sensor in the tank. The fuel float has no affect on when your light comes on.