Not entering an ID will assign a random one.
The timer will only show a clock and will not
work without a controller.
The controller with the same ID as the timer will be able to change its settings as well as view the timer. The two are intended to be used on separate devices.
Multiple timers and controllers can be on the same ID, but controllers may not sync properly. Reloading a controller page may also cause the settings to not appear the same as prior to the reload, and may need to be toggled a few times to appear correct.