I have used this method before on my spa. I believe that the second part after 1-2 minutes is really measuring TC and not CC. To get CC then you must CC = TC - FC. With a high CC, you will notice the solution getting darker over time. However, you generally cannot measure a CC of < 1 ppm since it is difficult to tell the difference in color. Even at high levels you do not get a very accurate reading. But then again all that you really want to know is that your CC level is bad and your pool needs a shock.