It's hard to say is it bug. On the screen it looks good (comparing to your min and max fuel economy). I need to take a look at your fill-ups. Fuel consumption was fixed and tested in many ways. It should be good.
Maybe you have checked fill-ups as full even when they were partially?
Please, send me your CSV and tell me what units are you using.
You should have your car's units set before adding any fill-ups.
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