Too little priming sugar

I just got the Brewing classic styles book and I was looking at the nomograph at the end of the book regarding priming sugar amounts.

The special bitter I made calls for 1.5-2 volumes of carbonation. According to this chart, I should only prime with 2.8 ozs. of priming sugar, and that's with figuring on the high side (2 volumes).

This doesn't sound like enough priming sugar for 5 gallons? I'm not doubting, I'm just looking for some confirmation for folks that have used this small of an amount of priming sugar.

I like lower carbonated beer and have used amounts that small, but it may turn some people off. I'd bet Samuel Smith ales are only about half as fizzy as a lot of macro brews.