i have a new comfortbilt hp61 been burning it for a couple weeks, absolutely love it. I cleaned it out today and noticed behind the glass door below the opening of the bottom of the door frame there is a metal plate with a knob and it slides left and right, if you slide it to the right it reveals 4 or 5 slots I’m guessing something for air flow. I never noticed it before and there is nothing online or in manual aboi