I will be glad to answer for all your questions and comments. We are developers and manufacturers of this light, so all your input will be greatly appreciated.
Next press - switch between Low(user) and HIGH: HIGH-user-HIGH-user-...
Long press (>1.5sec) - OFF.
So, for normal usage you have two modes - Low(user) and High. Short press to switch on, short press to switch between modes, long press to switch off.
User level brightness programming: Switch on, switch off (press key for >1.5sec) and continue hold the key (>5sec). After 5 sec light is switched on and start increasing light level from 2% till 50% and back from 50% till 2%. At any time you can release the key - this level will be stored as user level.
Strobe light programming: Switch on, switch off (press key for >1.5sec) and continue to hold the key (>5sec), continue to hold the key till full brightness programming cycle finished (15sec). After that light will flash 3 times. If you release the key during this flashes, strobe mode will be enabled (or disabled, if it was enabled previously).
If strobe mode enabled, you will have three modes: user-HIGH-strobe-user-HIGH-strobe.