@Isaac Summers can you check the link? I tried clicking on it and received a Page Not Found.
My guess is that you inputted appreciation into the equation. Over time, if a property appreciates, you will profit more than the (original) sales price of the property. If that's not it, then I imagine I'll need to see it to better diagnose.
Or maybe the profit is represented as the total profit found over the 30 years and they combined it into one number at the end?