Chins under a year should eat as much as they want, they are still growing and should not have their food limited. Once a year old most eat about 2 table spoons of pellets a day, if he runs out refill the bowl. Some people like to free feed, chins don't normally over eat, but I like to measure so I know when they aren't eating. In addition he should be eating roughly a handful of hay a day. Hay should be making up the majority of his diet, roughly 70-75%, with pellets making up the rest, along with treats.