same happened to me few months back
try filling of 1500 or 2000, the needle will go up...usually when i leave the car at low fuel then filling up of 500 or 1000, it doesnt effect the needle...although the car will give you normal mileage...its just the fuel wont show
and yea...when you drive above the range for 500rs worth of fuel..then needle will go even down
so get your tank filled up...and try to keep above last quarter