Are you referring to the lights built onto the motherboard itself or are you referring to lights attached to an ARGB header? I am not very familiar with newer ASUS motherboards but I've heard they might just be using ARGB lights for the on-board lighting on newer boards but I don't know what the zone size should be. ARGB lights operate as a chain, and the controller needs to know how many LEDs are in that chain. For ARGB headers you have to know the number of connected LEDs by looking at the device(s) connected, but for onboard maybe there is some parameter that can be requested from the controller that we don't understand.
Either way, you can determine this experimentally by entering a number, setting all LEDs, and seeing how many light up/change color. Repeat by increasing/decreasing the zone size until it is right.