In the long post, someone, Adrian?, pointed out that the on-board signal test only shows packets not the actual strength.
I posted a video there to show what my TIU does on power up, and different button pushes.
I considered adding a momentary switch to jump the 5 volt to calibrate the unit with as Stan pointed out. I'm not sure what's the best? I should have compared the 5 volt setting to the good TIU channel setting on the pot. I only did the "known good channel" calibration because I had already mounted the tester inside a case.