I don't agree raven... When he said, "that's what I heard," it appeared that he hadn't realized the magnitude of the laughter just yet. It took him a moment, and then at about 19 seconds he started to figure out that the audience is laughing AT him heartily. His facial expression changed (chin tenses up, lips clinch, eyebrows get more pronounced) and he actually appeared really irritated. After that, he started stuttering exactly as we've seen in the past when he's gone off of the teleprompter. I don't believe that HE intended this as it's interpreted but I have no doubt that his speech writer intended it as we understood it. He CAN'T understand even 10% of what he's reading or else he wouldn't say it. I think that this is no exception.