Every morning fuel meter of my scooter shows reduction in my fuel level from previous night fuel level.Initially i thought it could be some leakage issue I have analysed this but there seems to be no leakages nor there is any smell of petrol .I have noticed the similar behaviour at day time also after parking my vehicle for some time and riding it back.
You have not said how much of a reduction, so this is just some basic theory.
Fuel level gauges are for reference. They are not precise measuring devices.
That being said, while your scooter is moving, the fuel is sloshing around the tank making the fuel level float rise and fall. The gauge will only read what is an estimate of what it thinks is in the tank.
When you park the scooter, the fuel stops moving. So when you turn the scooter on again after time, the level appears to be lower.
After sitting overnight, there may be some contraction of the fuel as it cools from the previous day's heat. This simply depends on the climate you live it.
Your scooter probably doesn't hold a lot of fuel, so any small fluctuations will likely appear large on the gauge.
Fuel meters are usually designed to work when you scooter/motorcycle is level. Your fuel level mis-reading could be due to the kickstand or main (center) stand. When you use the kickstand the scooter will tip to the left, the fuel will go to the left side of the tank. When you use the main stand the back wheel is lifted off the ground, tipping the scooter forward. This will make the fuel run to the front of the tank. Either tipping to the left or forward might make the fuel gauge under-read. I've noticed this happen on a couple of my motorcycles.