First off let me say that I don't really know that this is a Rachio issue directly but I can say that they could make things considerably more "usable" for this particular scenario.
I have a PWS (HLFRISCOTX) that is using Raspberry Pi-based MeteoHub as the recording / reporting device. Unfortunately this software has the behavior of not resetting the accumulated rainfall counter exactly at midnight so typically after a day's worth of rain, the following day's first or second reports include the non-zero accumulated rainfall counter from the previous day.
For example, yesterday (10 Apr. 2017) the recorded accumulated rainfall was 1.47" and the last PWSWeather reporting looks like:
11:57 PM 65.5°F 63.7°F 94% 4.5 mph NE 5.4 mph 30.07 in - 0.00 in 1.47 in
Today's (11 Apr. 2017) reporting looks like (it was still lightly raining over the midnight boundary):
12:02 AM 65.5°F 63.7°F 94% 4.0 mph NE 2.0 mph 30.07 in - 0.04 in 1.47 in
12:07 AM 65.5°F 63.7°F 94% 2.7 mph N 4.3 mph 30.08 in - 0.04 in 0.08 in
12:12 AM 65.3°F 63.5°F 94% 4.7 mph NE 4.3 mph 30.07 in - 0.04 in 0.12 in
In this case once we roll forward to tomorrow (12 Apr. 2017), Rachio will officially record the "high water mark" precipitation for the 11th as 1.47" -- so effectively it record the same fainfall across two different days (10th and 11th).
This seems to me to be a fairly common data pattern that could exist due to clock differences, etc. so simply taking the "maximal" value for the day seems to be an overly simplistic way to view this data point.
With hot-weather coming on soon, I would like to not have to deal with manually adjusting things to work around the double water credit being applied to my landscape.
Let me know if this is not clear or if you need additional data to review.