Oh. When Kaylee puts it that way... Jamie is pleased that she thinks highly enough of him that he could do the work. And, to be honest, he's been feeling a bit at loose ends about the ship. He wants to help in some way, but just hasn't really found a place where he thought he'd fit in.

He's serious as well when he replies, "I do want to help ye, Kaylee. I just thought ye were joking. But...if ye think I can do it, I'd be willing to try."