OH2 Dimmer Item and extra parameter

Hi all!
I have wrot my own add-on for the some kind of hardware.
There is a dimmer that receives 2 parameters: brightness and running time.

Commands like ON/OFF/percent work well.
And now I have no idea how to pass the second (running time) parameter to it in sendCommand() statement.

Alternatively I can designe it to operate a JSON string, but it seems to me it is not elegant way.