How to adjust JP15 dB boost ?

[JP15]

I screwed around with the small dB boost pot in the back of the guitar and now I would like to set it up to factory setting of +20dB.
How can I achieve this ?
I have dB meter and a multimeter if this is anyhelp.

Thanks

 

[RAIN27]

Hi, just turn it fully clockwise and that's +20db.