Hi Tim,

Netro calculates the smart schedules based on weather condition, sprinkler type and other environmental conditions like soil types. If you selected Dripper/emitter for your zones, the zones have longer watering duration than other zones as dripping/emitter system is really slow in moving watering to the ground. 

Some zones are watered multiple times a day, you probably selected clay, clay loam or loam as the soil type which accepts water slowly, often as little as 1/4 inch per hour and that is why Netro breaks the watering into many pieces to avoid water runoff.