Question: How much db does the preamp circuit on a Luke III boost the signal?

just out of curiosity:
some say the preamp has a 12 dB boost, others say 15 dB. Some even say 20 dB.

On the MM product page it first says “15 dB Gain Boost Volume Knob” in the ‘Highlights’ section but in the ‘Control Function Diagrams’ section it says “VOL +20 dB” :confused:

So what is correct?

All the best