Mechanical line counters count revolutions and convert that into distance. I just looked at an Okuma reel and guestimated the diameter of the empty spool to be about 1 inch and the diameter of the full spool to be about 1.5 inches. Since the circumference of the spool is pi * diameter, a line wrap on a near empty spool is about 3.1 inches while the line wrap on a near full school is about 4.7 inches. That may not seem like much difference but 100 wraps at near empty is about 26 feet of line and 100 wraps at near full is about 39 feet of line. A line counter reel is going to count both as the same distance because the revolutions are equal. So as SuperDaveMT pointed out, you need to experiment to determine how full or empty a line counter reel gives its more accurate reading.
When jigging kokanee schools in the late summer where I fish, the fish are almost always at 80 ft, +/- 3 to 5 feet. We created a conversion chart showing line counter distance versus distance in the water. It worked but was cumbersome, and guests frequently forgot to make the conversion, so they fished well above or below the school. Eventually I switched to lighter weight spinning reels, pulled out 80 feet of leader and braided line, cut the 10# braid, tied in a foot of high visibility yellow braid, and put the yellow HiVis at the water to fish 80 feet deep. It easy to go up or down 5 feet and I can feel the knots on the rod eyes, so I don't even have to watch as the lure drops. I also use the same reels on faster rods for downrigger trolling and use the 80 ft marker to judge drop, etc. I have never had one of these knots break and use the same braid (but replace the leader regularly) for several years and hundreds of fish. I understand the advantages of a clicker on a bait caster for DR trolling but I like super light equipment for 20 inch kokes. We all like different things; experiment until you find what works best for you.
Good Luck
