Why does my receiver volume go from -db to +17db


On my NAD T 765 the volume goes from -90db to 17db. What does that mean? I thought 0db was silence and 35 t0 45db was an averave ambient level for a room.
georgeblaurock
If I had to guess I would say that 0 db is unity gain. Anything less than 0 the preamp is attenuating the gain of the source and anything greater than 0 the preamp is accentuating the gain of the source.
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