It's the Drew's Dosing pump, and it's has 4 rollers. (The other pumps only have 2 rollers I believe). I think they state the flow rate around 1.5 ml per minute, but each pump's rate can vary so you have to test it after you purchase it. I have 3 pumps and the flow rates are 1.2 ml/min, 1.6 ml/min, 1.5 ml/min.
Then like you mentioned... you just adjust the time the pump kicks on based on your flow rate, and how much you need to dose.
I believe I set my my pumps to kick on 5 times per day, and the time ranges anywhere from 8-10 minutes each time depending on the particular pump. It tried to spread the daily dose over multiple smaller doses throughout the day to minimize the pH effect, as well as to try and add soem stability to the levels vs a 1 shot dose each day.