Luxman L58a

Looking at restoring a Luxman L58a and when looking at the schematic I've found an adjustment pot in the psu that isn't mentioned in the adjustment procedure, anyone known what its doing? Please see attached pic
 

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Based upon the values in the schematic, I estimate nominal voltage as 23.9V. So, guessing 24V might be a nominal a setting? The 2.2K pot has modest adjustment range re R813 (33k) so the voltage should be within a few percent of 24V.

Estimates:

Q805 base voltage must be about 16.6V, base current assumed neglible.
Pot resistance 1.1k at center rotation, so current through pot and R813 is about 16.6V/34.1k = 0.487mA
So voltage across R612 is 0.487mA*15k = 7.31V
So, regulator output is 16.6V+7.31V=23.91V