Jackson,

Sorry about the full e-mail. You can also e-mail me directly.
PCGeek and PatL have answered correctly. The duty cycle (Purifier %) will indicate ON or OFF, depending on if the cell is energized or not.
The position of the red cap does not matter. You're only using two of the three pins so cap off either outer hole and use the other two.
Finally, it will not affect the SCG to shock the pool if needed. Remember, most people on here recommend using a manual shock to oxidize the combined chlorine from after a pool party or bad weather, rather than using up some of the cell life by doing a BOOST mode. Smart advice to optimize cell life.

Regards,