Want to tap line level off of a reciever. Help me id these pins?

Top of the board main volume pot.


Bottom of the board associated pins.


I want to tap off of this Right Pos/Gnd and Left Pos/Gnd to supply signal level to a separate chip amp.. If it were merely the case that there were four pins labeled Lin and Rin I would just id the grounds and be fine. But I'm puzzled by the fact that there are five pins labeled with four IDs.

Any help here?
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