No it just means that it is set to output the full 20 bits. By pressing the DIGITAL OUT button, you can toggle among Out 20, Out 16 (this truncates or chops the last 4 bits) or 16 Dt, which adds dither when cutting off the 4 bits, resulting in less distortion introduced into the signal.
By the way, it is NEVER a good idea to turn the machine off with a tape in it....the tension will "relax" when you turn it off, and the tape will likely come into contact with the still-spinning drum. As the drum grinds to a halt against the tape, the heads can clog. Done often enough, your heads will grind down and you will need a new upper drum (the part that spins and has the heads in it).....