Hi John,
You have around 14 litres for the tank – 3 gallons. I’ve been monitoring my consumption and it’s between 60 to 70 mpg – or about 100/120 per 7 or 7.5 litres (depending on how “nice” I’m being).
Things may (will) change once the first service gets done, tick over reduced & time to explore the rest of the rev range.