The commercial timers allows for automatic running of ads should you so choose to have that functionality. The time between when this adverts are run is determined by the time you set, which by default is 30 minutes. You can also choose to have a message sent to the chat before this ad is run and when the advert has finished playing as well as the length of the advert you want to run.
Once you have adjusted these settings you can press "start timer". This will then begin counting down and once it reaches 0 it should run the ad for the length of time you set and hopefully reset itself to the time you set, beginning its countdown again. As I'm not a partner, however, I don't know if this is actually the case. I am just assuming it will do this.
Thanks,
Dante557