He kissed her back. BUt he couldn't help but reply after she started explaining things. "I know that now, but then I was very nervous. You can't have missed that," he said. "I just needed to get to know her a little better. And I figured that would take some time and effort."
He knew from the way she looked at the ring, she didn't think she deserved a ring as beautiful as this. And he rather thought the ring wasn't beautiful enough in order to match her beauty.