You choose how many ML, in how many times a day and at what time of the day.
The cool thing about it is there's 3 presets you can configure and choose from.
I made 2 custom configurations where it does a high dose, medium dose and low dose, depending on how fast my corals consume the alk, amino and ca.
I tried this with kalk, but you have to pay attention to the kalk buildup, the tubes will need to be replaced or cleaned every month.