So...Cas visited the vet yesterday, just a checkup to make sure everything's good, and it is (he's healthy as a horse!), but here's the thing. Vet ages him at about 8 weeks due to his development, and based on my research that's what I thought too. He's pretty fully feathered (95%) minus just his head and a small portion of his neck. He weighs 8 pounds! My problem is that the math on his age isn't adding up?
I got him on April 25th, and due to his size, his fresh umbilical, sleepiness, etc led me to think he was no more than 2 days old and still recovering from hatching, but at that he should be going on 6 weeks old this weekend not 8 weeks old, and his size and feathering don't seem to match with him being that age? Two weeks is a big difference in a gosling, so how do I know which is right?

(The day we got him, April 25th)

(Taken today June 3)
Any ideas who is right? Is it possible he was older when I got him and just small?
I got him on April 25th, and due to his size, his fresh umbilical, sleepiness, etc led me to think he was no more than 2 days old and still recovering from hatching, but at that he should be going on 6 weeks old this weekend not 8 weeks old, and his size and feathering don't seem to match with him being that age? Two weeks is a big difference in a gosling, so how do I know which is right?
(The day we got him, April 25th)
(Taken today June 3)
Any ideas who is right? Is it possible he was older when I got him and just small?