I know what mean about getting magnet polarity in the correct N-S pointing direction. I have similar Hall Effect tachometers on two of my 12" and 7" swing lathes (see Homemade Metal Lathe Digital Tachometer - HomemadeTools.net and http://www.homemadetools.net/forum/m...3147#post15859 .
The eBay sellers luckily provided the wiring schematics at the auction website pages so no need for a translation. Also Randy Richard in the Shop (see his YouTube channel ( https://www.youtube.com/channel/UCme...AeH21q-xcNwdfw ) warned about getting magnet N-S orientation set correctly before gluing in place. Otherwise the Hall Effect sensors won't work at all.