Judging by the troubled look on Sam's face, he doesn't quite believe her reassurances either. After all, Gandalf had been brave, and he hadn't been rewarded at all. But that hardly seems like something to bring up when Hermione's trying so hard to make him feel better, and he smiles up at her gratefully. It does help, a bit.

"Thank you, Miss Hermione," he says sincerely. There's a pause, and then he adds, his tone lighter, "Though that's a funny way of putting it - being the bigger person! It hasn't made me bigger at all."