Hey @Francisco Núñez,
When you use the Fuel Tracker in Geotab Drive, it creates a FuelTransaction object in Geotab. These FuelTransactions can be associated automatically with a FillUp in Geotab. If that happens, you'll see the associated FuelTransaction when you view a FillUp on the Fuel and EV Energy Usage page. If it doesn't automatically associate with a FillUp (because there wasn't a calculated FillUp at that time), then the FuelTransaction will get its own row in that page and if you click into it, you won't see a FillUp associated with it. I hope that helps explain the relationship between the Fuel Tracker transactions and what you see on that page. And yes it can help the estimate for fuel consumption, but it's much better if you just enter the tank capacity on the vehicles, then the fuel consumption will use that and the percent change to give you a much more accurate data set.
Thanks,
Tucker