@Fitnessmentor, You make a fair point regarding the way we calculate water usage.
With Flow Sensors (/Meters) now in Beta testing, we're hoping to do one better than calculating, and accurately measure the water used.
However, I do realize the cost of purchasing & installing a Flow Meter can be prohibitive, so I offer that tid-bit only to emphasize where our focus lies right now.
The nozzle count input is definitely an idea worth tracking, and has been suggested by others as well - thanks for putting it out there!
Just to let you know, we are listening to all feedback and suggestions - yours is much appreciated.