Depending on the size of your system and what you want to accomplish, there are lots of ways to dose kalk.
In my system, my ATO is a separate function from my kalk reactor (although they feed from the same RO/DI storage vessel). I use my RKE to control the stir pump (4 times a day, 1 minute each time) on my GEO reactor, and it also controls a BRS 50 ml/min peristaltic pump that doses about 1 cup of kalkwasser 8 times per day. My ATO is a gravity fed system that has solenoids controlled by a dual float switch. It basically fills in what ever isn't covered by the kalkwasser, usually about a gallon per day.
The total of 8 cups of kalkwasser was a volume I had to tune to figure out exactly over a period of time and will change as I add water volume or additional corals to the system. I also have an "alarm" function set that will prevent the reactor from feeding the system at all if the pH gets too high.
Some folks simply run all kalkwasser for ATO. I just choose to use a controlled volume separate from ATO so I can make adjustments without potentially messing with my overall water level.