For those that have their precipitation rate (inches/hr) and their GPM usage from the meter and need to figure out the square footage so the app shows the correct water usage, i did some simple algebra and converted the Precipitation rate formula so you can easily calculate square footage you need to put in the app:
SQFT=((96.25*GPM)/PR)
I have created a quick spreadsheet in google docs to help those who dont feel like pulling out the trusty calculator to do the math for each zone. Download your own copy of the spreadsheet to do the calculations (the formula is already in the Square Footage Column, so simply enter your precip rate and GPM and it will do the math for you): https://drive.google.com/open?id=1danaMKyuma94IY0DN_wJs0DIu_gGgLWf8Fa0k2StKCU
I dont know why this isnt a calculator on their support page. If GPM manual entry is not going to be in the app, then at least put it on the website so users can easily find the way to make the calculations themselves.