I'm new to Rachio and unless I'm totally misunderstanding this I think these two are very confusing.
Custom Nozzle is area where you enter specs for your custom nozzle that isn't out of box with Rachio, at least that's what it looked like. And when you setup your zone you use the custom nozzle you setup. But what if you have 10 of these spray head in that zone? What if you have mixture of spray head in that zone?
Since zone setup doesn't allow you to setup multiple nozzles with their quantity, I believe what the app is expecting is for Custom Nozzle to be configured with precipitation rate (manually calculated in/hr of all the spray heads in the zone) and zone to use that Custom Nozzle.
If this is the case then I would suggest the below:
1. Instead of Custom Nozzle, in/hr value of the zone should be entered with in the zone setup.
2. But to have the app be more intuitive, I would use the custom nozzle to be configuration of that specific nozzle and it's spec. Change the Zone setup to allow for multiple nozzles with it's quantity to be specified. Then zone setup can calculate the in/hr rate for the zone.
On my first pass through the setup I had setup my custom nozzle to be a specific model with its' specific spec but since zone setup didn't account for # of heads in that zone my schedule came out to 5+ hours of watering. But after I setup custom nozzle for each zone and accounted for all the spray heads in the zone and the area that it covered for the in/hr calculation then the schedule came out to 2.75 hours which seems more reasonable.
It's not very intuitive to know that this is how your app functions so to give the user the best user experience option 2 above would be best but option 1 could be a quick fix to resolve this confusion.
Also it seems your schedule does not automatically calculate the change in custom nozzle or zone setup. I had to delete and create new schedule to have it use the new parameters. Again not very intuitive as I would expect it to use the updated values automatically.