Hi Gregor, 

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. 

You can go to Settings->Restriction to create a restriction to strictly restrict the watering time.

Thanks,

Wency

Netro Support