This is the one of the Two pins of the encoder. If the encoder appears to go the wrong way you can either
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1/ Swap the wires on the encoders (Open case, turn on soldering iron, find solder, find flux, etc. . . )
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2/ Change the numbers in the webconf.
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This is the flexibility on offer but obviously with such flexibility you have to be very specific.
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It is unlikely you will get it right first time because you have the possibilities of getting both the hardware wiring AND the configuration wrong and this can be very frustrating