Guides are guides, and just that, IMO. Mind you, I'm not a veterinary dietician or anything like that.
Our kitten is on the opposite end of the spectrum from you. He's 9-months old and weighs about 12 pounds (large breed), very active and still growing, and he only eats ~4ozs a day, sometimes less. For the longest time, we tried giving him more, but he only wants to eat a certain amount over the course of a day. We were a bit worried, but figured he'd eat if he was hungry, and stop if he wasn't, and as long as he was healthy and growing, it didn't matter if he was below the average in terms of his eating.
From everything I've heard (being relatively new to raw diet), cats on raw diets are very good at maintaining healthy weights. If he's hungry, I'd say let him eat more! If he starts to get too heavy, then maybe re-evaluate.