You could absolutely use that measurement if you followed their installation instructions for spacing, water pressure etc. To get (maybe) better in/hr measurements related to how you spaced and adjusted the sprinklers: put straight sided, flat bottomed containers (most often recommended are tuna cans, for example) on your lawn – maybe along a line in the middle. Be sure to capture some overlapping and not overlapping (if there are any) spray areas. Run the sprinklers for 15 minutes (1/4 of an hour). Measure in inches the water in each container. You could average those results and multiply by 4. This will give you the application rate in inches per hour. I recently did this and got 1.1 in/hr, just a tenth more than what Rachio had as a default.