Leaving ground balance on default 0 is a perfectly good way to start out.
If you aren't sure if you need to ground balance (since the Equinox does not have a mineralization bar or graph on the display) here are three ways to tell.
When you have finished your startup sequence, sweep the coil over the ground you want to detect and listen for lots of really short clicks and pops that may or may not register as a numerical target ID. If you hear several with each sweep you either have lots of tiny man-made iron or metal fragments at your site or you have ground mineralization. You could even have both! If you hear nothing sweeping the coil over target free ground or only an occasional click or pop you are good to go with the default 0 ground balance setting. This is in the manual which makes for a nice bedtime story. If instead you hear tons of jumpy audio and see lots of wildly fluctuating numbers on the display, you have too much sensitivity for the EMI in the area. Lower the sensitivity until the Nox quiets down and/or move to another area away from the EMI source if you can find it.
A weird way to see if you need to ground balance is to find some target free ground then press and release the pinpoint button. If you are not over of near a target you should hear nothing except for maybe a steady, faint background hum. If you hear lots of "boing" like sounds as you sweep or raise and lower the coil (if you get the pinpoint function to work properly.......it does take some practice and reading of the manual repeatedly especially anything in the blue boxes) you probably need to ground balance.
The easiest way is to press the settings button again after noise cancelling (if you are not over a target) which puts the Nox into ground balance mode. As you gently raise and lower the coil you may hear nothing or a steady faint background hum=good. Hit the detect button and go detect. If you hear a lot of "boing" type audio you might want to press the accept/reject button while raising and lowering the coil until you hear a beep and the number on the screen settles. If you are not comfortable doing that you can also just manually raise the number from 0 with the - and + buttons until it quiets down. Either way, you just ground balanced the Nox. If you still aren't sure just hit the - button until you get back to 0. It is all in the online manual. It takes less than 30 seconds after a little practice.
If you notice a squiggly line under the Wi Fi/Bluetooth/Headphone icons in the top right corner, that means you put the Nox into tracking ground balance mode. Just go back into setting/ground balance and press the accept/reject button again so the squiggly icon goes away and hit the detect button to return to detecting.
So, an experienced user will probably have this sequence if their site has iffy mineralization or EMI. It takes less than a minute with practice.
Turn on
Select detect mode
auto noise cancel
check for ground noise
auto ground balance if needed
possibly lower sensitivity if EMI or ground noise is still present, if not, raise sensitivity until the Nox audio gets unstable and back off a click
go detect
find some great targets (and some trash)
Jeff