Caption: A generic Hertzsprung-Russell (HR) diagram showing the luminosity classes of the luminosity class classification scheme.

Note spectral type is a correlated with photospheric temperature which increases to the left and absolute magnitude is a proxy for luminosity and runs the wrong way---higher number is dimmer, lower number is brighter.

But 5 magnitudes (down/up) is a factor of 100 (up/down) in brightness (here = radiant flux or spectral flux)---fact.

The luminosity classes are bands on the HR diagram and NOT partitioned by by fixed amounts of luminosity, but just by average amounts for each spectral type.