The ballast should run the lamps at exactly 1.00 ballast factor, which means they are at their nominal power and nominal output. If the number is higher than 1.00, then the ballast is overdriving the lamps, changing their spectral output and increasing output wattage (and therefore PAR). If the number is lower than 1.00, then the ballast is underdriving the lamps, also changing their spectral output and decreasing output wattage (and PAR).So in laymans terms this means....?
Just looked up the data for 54w lamps and 80w lamps to round everything out.
Dimming
2x 54w - 1.00
1x 80w - 1.00
Non-dimming
2x 54w - 1.00
1x 80w - 1.00
So those will run the lamps exactly at spec. For the 24w non-dimming ballast above, it will overdrive the lamps by 12%, whereas the dimming 39w ballast will underdrive the lamps by 16%.