Retrieving Flow Sensor data via API

I am using the API to create a super simple client to help me when I change my watering schedules. I have a flow sensor attached that seems to be working OK and I am trying to retrieve the calibrated gallons/hour for each zone.

However, I can’t see that data in the json object that I get for the zone.
The info appears when you view the zone through the web app, so I imagine it is available, but perhaps not exposed through the rest api.

Is there any way to retrieve the calibrated gph for each zone?

Thanks in advance!