When you get the instructions you will see a hand sketched picture of the sensor and magnet bolt position. You want to move the sensor so that the tip of the sensor picks up the magnet! This results in moving the sensor a half inch futher away from axle to get the unit to work accurately. I have advised many TT members on this and it does work for all of them as well.
OK, the computer showed up today, & it appears that they fixed their instructions, Have a look for yourself & tell me what you think.
Trail Tech Computer Installation Instructions