It has a 20 litre tank so the ranges would be 295, 339 and 365 miles at 67, 77 and 83mpg. You wouldn't want to run it dry though, so allowing 2 litres for not quite filling it and finding a garage to fill up would give you 265, 305 and 329 miles respectively. I'd be interested in what the fuel consumption drops to when pushed to 80-85 mph.
When it gets to the last bar you have 4.5 litres left, when the last bar starts flashing you have 2.5 litres left, if you trust the spec sheet.