Netro algorithm encourages longer water time and less water frequency, which will help growth of the roots. It will also break long water time to several small slots to prevent water runoff.
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.
If you want to make sure all the watering to be done at a certain time. You can create a restriction through Settings->Restrictions,
If you create a program or restriction, Netro will strictly follow the watering time and duration, however, preferences will not. Netro will try to water during your preferred time. However, if Netro believes your watering is not enough, it will still water your zones regardless of you preferred watering time.