The advanced zone setting you’ll need to look at is the Nozzle In/Hr setting. That can be used as a drip rate, but you’ll want to look at how to calculate that using the Drip Emitter Calculator. Basically it is converting Gallons Per Hour that most drip emitters advertise to Inches Per Hour. For the zone area variable in the calculation you may not want to use the total area of the zone but the area under the most important plant you want to keep alive (e.g., measure its radius and use pi*r^2 to get its area that needs to be irrigated). Also use the emitter GPH for that plant. If you have all sorts of different GPH emitters on a single zone and many types of different plants, things get challenging and there’ll be some thinking to do.
https://support.rachio.com/hc/en-us/articles/115010379587-How-do-I-calculate-my-precipitation-rate-