Hey Troy,
The short answer is that we ask you to let us know when you apply the product in the app and then we adjust the crop coefficient based on a number of reduction factors, taking into account seasonality. An active microbiome creates physiological changes in the lawn, including increasing soil porosity and increasing the grass’s transpiration efficiency. Effectively, this reduces the crop coefficient (relative proportion of daily reference ET that the plant transpires) during the application.
I believe you might be in Koppen climate BWh. In that region, we believe we can get you another ~2.2 skips/45 days. Attached is a graph that shows the growth rates for cool and warm season grass and the microbiome activity (assuming an ample food source for it) over the months. You can see how a microbiome-deficient soil puts your grass at the mercy of what its root ecosystem can do on its own, and getting an assist from and active microbiome allows it to thrive at more extreme temperatures.
With regard to your second question. At this time, a thrive subscription is tied to one Rachio controller. @simonhill (our VP of Product) and I were talking through this this morning and we might be able to get around this dependency soon and can get back to you on that.