1. Netro calculates the smart schedules also based on soil type. 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 we break the watering into many pieces to avoid water runoff.
2. For your 4th zone, you can add rest time to avoid runoff through Settings->Preferences->Scheduling. If you think watering too much, you could try customized mode to adjust watering by providing the preferred moisture level and flow rate of your sprinklers. You can also create programs to water this zone separately during the day.