In a Restaurant
You’re in a restaurant with a dozen friends. Your waiter (sorry: your server, Trevor) just finished spending ten minutes taking down everybody’s order. When he’s supposedly all through, he looks up at nobody in particular and says cheerily, "Okay, so that’s five broccoli salads, right?"
At this point, inevitably, someone at your table who isn’t thinking clearly immediately jumps in and starts to take a count. He may go around the table, or ask for a show of hands, and all the while Trevor is standing back happily while your friend does his job for him and everyone else rushes to cooperate as confusion ensues.
Instead of letting him get away with this, you should turn to Trevor and say, "I’m sorry; were we supposed to be keeping count? If so, why don’t you take everybody’s order again and I’ll keep tabs."