I agree with @cfwiggum. There are two things in play here.
- How many gallons of water used in the time that the sprinkler system was active. That is good to know for billing purposes etc. In some jurisdictions, you pay x amount for y amount of gallons and then x + z for anything over y. Since water consumption in the home stays pretty steady, I know how many gallons I have to work with for landscaping purposes.
- How much precipitation is applied to the yard. This is where the catch cups come in. This will let me know if the water is distributed evenly, how much evaporates etc.
When rachio reports gallons used (and saved), I believe it should be based on the figure described in (1). When it needs to calculate how much to water it needs to factor in the figure from (2).
Those two are not the same IMHO.