Meanwell LDH-45 LEDs Glowing When Controller is Off
The meaning of that statement is pretty clear, the minimum output voltage is the input voltage. 

So to get less minimum brightness you can either use more LEDs in series or lower the input voltage (or both). Too few LEDs and they might be damaged. 

The topology probably looks like this (from Wikipedia commons): 



For minimum output, the switch is always open so the inductor and diode are in series to the output. It's possible the diode is actually another switch.