This pool does not pay out everything you earned in a given 24 hour period. If you were to stop your miners cold, you're still going to get paid the next day, or even 2. As I understand it, there's a buffer that builds up due to the time it takes for blocks to mature, to transfer funds to exchanges, do the exchange itself, and transfer them back out.

In order to understand what you're making in a day, switch one of your rigs to a separate address, and run it for a specific amount of time (the longer the better), and then disable that address. That way, you have real numbers with a known amount of time, and you can calculate how much you're making per unit time.