Sonos volume setting

Setup, Configuration and Use Beginners
1

I switch my sonos on by increasing the volume to a certain level with a delay of 5 sec between every increase and that is working fine.
Only I don’t understand why the volume is always 1 lower than I configure.
I the code below the value of HuidigKeukenRadioVolume = 11 and SonosPlay1KeukenVolume = 10.

        SonosPlay1KeukenVolume.sendCommand (HuidigKeukenRadioVolume.state as Number)

Any idea?

2

Find below some more code to explain my question

       HuidigKeukenRadioVolume.sendCommand (HuidigKeukenRadioVolume.state as Number + 1)
       SonosPlay1KeukenVolume.sendCommand (HuidigKeukenRadioVolume.state as Number) 
       TimerRadioVolumeKeukenAan.sendCommand(ON)

after adding a delay it is working

       HuidigKeukenRadioVolume.sendCommand (HuidigKeukenRadioVolume.state as Number + 1)
        createTimer(now.plusSeconds(1),[| 
            SonosPlay1KeukenVolume.sendCommand (HuidigKeukenRadioVolume.state as Number) 
            TimerRadioVolumeKeukenAan.sendCommand(ON) 
        ])

Can it be that the line
HuidigKeukenRadioVolume.sendCommand (HuidigKeukenRadioVolume.state as Number + 1) is not processed before SonosPlay1KeukenVolume.sendCommand (HuidigKeukenRadioVolume.state as Number) is processed?