"But I need to finish something"

I was getting ready to close the computer lab so I could go to lunch, and I told the students, "Ok, you have five minutes to finish up, because I need to close." Ten minutes later, they're still not packed up. So I restate that I'm closing. Nothing. As if I hadn't really said anything. Not in a disrespectful manner, it was more like they were in their own world.

So I again say that I need to close up. One of them says "Jeez, are you that hungry that you're kicking us out?" I had to say something. "This is my lunch time. I already gave you more time than I was going to. And you're not even doing work, you're shopping online! If we held you in class for even a minute past time, you'd complain. Now I can't even take my own lunchtime? WOW!" But I said it in a joking manner. They got the point, and got out.