It certainly should not burn wood at 0.3% power. It seems as though your laser is just not responding to PWM signals. I don’t have a Universal Engraver 15w Blue CNC Laser Engraver. Perhaps you should start a new topic and see if somebody else has an idea how to get your laser to respond to lower power levels.
(If it was an Ortur Laser Master 2 I would say it is a Control Board problem as they apparently had a bad batch recently and when they fail the laser just comes on full strength all the time. )