You stated:
"A example is my G/B is 36 in one spot then I lower the number down to 32 by pushing the - button and that makes the audio rise just enough to make it more sen. to gold and quieten the machine down a little when you are in the trash and iron. .... Now is that a positive G/B or a Negative G/B. Hell I don't know and don't care but I do know it helps my machine hunt better in the iron trash and makes it just a little more sensitive to the gold as I am really a water and beach hunter."... Yes, making a shift like that, from any larger # to a lower number (ie: 36 to 32) is making a positive adjustment to the GB.
However, your ground is much less mineralized than mine and you might get away with that much GB shift. Not so here, and I encourage a "right on" GB in most applications. I have found that the X-Terra 50 and 70, like many other makes and models (not all) that provide a manual GB adjustment can have some operational issues if the GB is set either too positive or too negative.
I hunt very trashy sites most of the time, and when I have hunted this past week, where a GB from 14 to 21 might be required to be on-the-mark, shifting too much either way gave me some problems.
What I do know is that Minelab needs to shake a leg and get us a smaller-than-stock sized coil!!
Happy Hunting to you.
Monte