Hi- nThe reason some people are allowed different amounts of Phenylalanine in a day has to do with things like their weight, age and how much phe they’re personal body can handle. For example me and my sister are allowed 300 phes (or 20 exchanges), mainly because we just can’t handle that much. As for the whole level things, I’m not positive about that, I know that generally it is 2-6 mg/dl but it is also different for many other people. I know someone who was told to keep his levels between 5-8mg/dl and when your pregnant some doctors want your levels to be between 2-4mg/dl. It might just be because your child is younger but I’m not 100% sure. It’s like with everything in the world, nobody is going to handle their childs school exactly the same right? Some parents have their children do their homework once they get home and others don’t mind, life in general is just never 100% the same for anyone and it’s the same with the PKU diet. Doctors are still humans so they’re going to be alittle different on how they handle things. nBreanna Hope this helped alittle.