This is how much the population increases from time zero to time seven. Now you might say, well, wouldn't that be the town's population? Well, that would be the town's population if they had no people at time zero, but you can't assume that. Maybe the town got settled by 10 people or by 1,000 people or who knows whatever else. So right over there. And this is taking the derivative of the rate function, which is, it's actually a little hard to think about what is this. This is the rate of change of the rate at time seven minus the rate of change of the rate at time two.