I think the amount to give as suggested by the guidelines on most packaging, the range varies so much. Willow is a female working cocker and she weighs 11.5kg (ideal weight as suggested by my vet only the other day) so your little one being male might weight slightly more fully grown depending on his frame, obviously this is only a guide.
We fed Willow 4 small meals of between 25g and 30g of kibble.