Is my puppy anorexic?

I’d greatly appreciate some help! I just got my 8 week old miniature dachshund. He is wonderful but will barely eat- especially the food his breeder had him on (hills science) I’ve been switching him to Carna4 and he seems be more enthusiastic about that. The thing is, he still never finishes his food. I want to give exact calculations. I try to feed him 2/3-3/4 cup of food every day. After he “finishes” his meal, I remeasure to determine how much he eats. He is eating roughly 1/3 cup of food the whole day. Is this enough? He is only 3.4 lbs but the calculations that the breeder gave and the recommendations on the bags of food have him eating double that. Can 1/3 cup really be enough for him? He is eating 2 tablespoons or so every meal.