Dimmer rotation span wider than the light intensity span
Your LED's are not capable of a full 360 turn on the dimmer switch. LED's require a minimum voltage to pass thru to light them up. Your dimmer allows a much lower voltage thru than the LED driver can convert. One way to test this, is to put a regular incandescent bulb in the socket(s) and try your dimmer switch. I am not aware of any LED bulbs yet, that can dim so low that they barely shine.