Most Helpful Guy
Well that depends on whats your phisque type and etc.
Or maybe he's never seen d's ;p
Most Helpful Girl
Perhaps he means they are bigger than he's use to.
Maybe he is used to having a girl with a A cup.
He also probably means, they're "big enough for him".
That doesn't necessarily mean it is above average size... but he means he is more than contented with the size of them.
As long as he isn't saying they are too big in a negative tone, I'd take the compliment and move on :)
Whatever, he means.
Just take the compliment