I think of the number as representing "cooling power" since that's what the machine's purpose/function is. I had been unsure about this for a number of years,

I think of the number as representing "cooling power" since that's what the machine's purpose/function is. I had been unsure about this for a number of years, until one day I decided to check by slowly turning the knob to both extremes and listening for when the compressor kicked on and shut off.