The USB ammeter is not 'used for tuning the sticks'. It is used just to verify that you have good power and what the load is so you know if your powered hub can supply what is needed.

The adj pot freely spins around but has just the 1 track so yes it resets to zero every 360-deg. Do NOT adjust it with power on. Looking at the dial as a clock and with the flat edge as reference the flat should be between the 15 minute mark (default) and 30 minuted mark. Mine is about the 20 min mark and happily runs 575MHz.