Help: 8 year old Trying stimulant for the first time

my son is 8 years old and we tried the non stimulant route first of meds but that was no help. So the doctor prescribed him a stimulant for his ADHD Quilliviant XR 2mg in the morning. We started today and the medication did nothing. He’s not focus at all and still hyper and day dreaming. I feel like 2mg is way too low for his age and weight. he weighs 68 pounds. I might be wrong bc i’m not a doctor but it doesn’t make sense. his doctor said after the first week of 2mg then go up to 4mg. which i think 4mg will still be to low. Has anyone delt with this medication before ? Any side effects? any advice?