Hi @sbillard, good evening. You ask a good question.
For each zone, the Iro needs to know the precipitation rate at which water is applied to the lawn, pot, etc. At first glance, it does make sense to configure this number around the number of heads, however, each head can have a different type of nozzle/insert which makes the math around output per head tricky.
The software isn't calculating the number of heads, but rather it's using the total water being applied by the heads/emitters, etc (as a whole) within the given area (sq ft).
This article does a great job of explaining precipitation rates and ways to calculate it on a zone by zone basis.
Yes, but no -- pots and drip zones in general are usually watered with emitters and bubblers. As such, the coverage area is very small due to the point source emission of the water. You'll need to take the total water output to each pot and the surface area of the soil at the top of the pot to calculate the precip rate.
I hope this helps. Please let us know if you have any other questions we can help with. Happy to help calculate your custom nozzle precip rates if needed.