CZ-21/CZ-3D advantage to run slightly positive or negative?

Any of you CZ-21 users notice that if you are able to operate on ground balance 10 the machine is actually a little deeper.It seems more so in the pinpoint mode than auto tune,and just a tad in descrim mode.Dont really know why that is.Now when I ground balance the detector with the bobbing method in auto tune mode and I start out on 10 ground balance and sensitivity is around 7 the machine goes quite as coil touches the ground.Turning the ground balance to 1 and the detector gets quite loud when it approaches the ground.In my ground the sound balances out at 6.5-7 on ground balance dial.Now my questions are my ground will alow me to run on 10 GB but does that mean I m running the detector slightly negative? I always heard for that extra inch or 2 you want to run your detector slightly positive;slightly rise in tone as the coil nears the ground during the ground balancing.But my detector is deeper when just set on 10GB.Why is that.If you can run your detector as close to 10 GB on the dial without chatter does that mean then your ground is quite mild?And or is it bad ground the closer you are to 1 on GB knob? I imagine this should all apply to the CZ-3D models.Im pretty sure the 21 is a water proof version of the 3D without the enhance switch. Hope this doesnt sound confusing and thanks in advance, Steve

Again it was told to me years ago by a Fisher tech where the dial number ends up does not neccesarily mean if the ground is good or bad...basically how fast it changes does..not being a tech...just a groundpounder perhaps some knowlegable forum member can add further info..

To me to ground balance positive the threshold doesn't stay the same but is set to be a little higher as the coil goes to the ground and of course negative the threshold would be higher as the coil bobs up from the ground using the bobbing method which is the most accurate.

Imagine setting slightly negative a tad could help on a saltwater shore to handle the enviroment and setting a tad positive on good ground could give some more useable depth but be careful either way as it could backfire if you try to set too negative as you may lose a lot of depth and of course small jewelry in doing so and in setting too much positive could cause adverse masking and lose targets close to junk...personally I try to set spot on but have read where small changes either way could be benefical.....