Knitting Row Counters Guide

I got this row-counter in my beginner crochet kit. It does not explain how to use it. How does this thing work? I can manually switch the numbers, but what is the

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One of you posted this row counter idea! : r/knitting

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Knit Counter, 4 Pcs LCD Electronic Finger Digital Counter with Knit Counter Knitting Crochet Stitch Marker Row Counter, Mechanical Manual Clicker Number Lap Tracker Counter. by ILouxNei