Recommended Watering Duration Irregularities

I created a new schedule, included a single zone, and initially Rachio recommended a watering duration of 42 minutes. Five minutes later, I changed the root depth of the zone, from the default 12 inches down to 7. Because Rachio didn’t update the watering duration after I made the change, I deleted the schedule and created an exact copy from scratch—just because I was curious what Rachio would recommend.

I was surprised that Rachio now recommended 45 minutes.

Why would Rachio recommend 42 minutes for a root depth of 12 inches, but 45 minutes for a depth of only 7 inches? My logic tells me I would need to water for a shorter duration when the roots are shallower.

Schedule type: fixed
Zone type: Desert adapted
Plants: recently planted succulents
Sprayer: drip line
Interval: fixed at every six days

Bump. Hoping to get a reply from someone at Rachio, or someone in the know, please.