It is my understanding that it is very accurate but it only measures the fuel used by the engine. You have to remember what you have used in the generator and aqua hot then subtract those gallons as the Aladdin system does not track those gallons.
I have tried to compare my actual usage to the Aladdin and it seem to be very close especially on trips where I do not use the generator or aqua hot.
2007 Monaco Camelot 42' PDQ
2013 Lincoln MKX - Roadmaster Falcon 2 - RVi b
rake - TireSafe Guard TPMS