It's been awhile since I read about bikes, but the fuel economy is incredibly bad for something so small!
It's a motorcycle review, much like their car reviews, they're probably more rev happy than the average rider. In a pure city environment, the 300 would do more like 3-3.5. Constantly rev that engine high or take it at high speeds and the fuel consumption jumps to 4-4.5.
When I rented a CB300F a couple of months ago, I fell into the latter territory -- 4.4 L/100km pinning it at speeds I won't mention here. To the Imperial folks, that equates to 66 smiles per gallon. I'm expecting the Puig windshield Wing's selling me to help with that number on my cross country trip.