Ersan, previous UTCOMs hadn't got fuel level input signal. Fuel tank level was calculated based on injector signal and fuel tank capacity defined by user. So, just like in old version, you have fuel consumption taken from fuel injector and vss signal, then those data plus fuel tank capacity gave you fuel level.
Thas solution required tho to remember each time filling up tank to put numbers into UTCOM.
Version 3.0 Pro give some chance that if fuel tank floater gives analogue output (range 0-24v depends on type of vehicle), then after initial setup (see above) and set up fuel consumption, then UTCOM can co-relate initial tank floater voltage with amount of fuel input by user. Then even if you forget to set how much fuel you filled in at petrol station, floater signal will give you rough estimate.
That's how I understand this additional feature, maybe wrong.
Another question is to find out floater signal, voltage and... is it progressive, or different equation? Or is it just a switch 0>1 (full>empty) Legnums. It may simply don't work.
Remember, UTCOM is designed for all broad range of vehicles, some features won't apply to Legnum.