G'day Bronc.
Looking at the video it does sound like mineralisation, but because you are pushing down over the signal it is difficult to tell. The only way to pick up a signal is when you swing the coil from side to side which you cannot do with the way the hole has been dug.
It is possible that the target is to one side of the hole you have dug, so the signal is getting a little louder but not like you are over the top of the signal.
First up, widen the hole.
Tree roots are notorious for giving a signal on the GPZ.
Since the signal is getting louder it is a good chance to be a metal target. I suggest you dig about another 300mm all the way around the hole and about half the depth of the existing hole. If the signal doesn't increase in volume then it is most likely ground noise, and if it disappears then you have dug it out.
Sometimes the signal will disappear when the mineralised ground is broken up. Once I dug down about 300mm and the signal never changed, then I knew it was mineralisation.
If you even suspect that the signal is a target, don't give up until you are satisfied you have dug down deep enough and the sound hasn't increased, or you hit a tree root or the target.
Especially since you haven't been detecting very long, dig everything. You need to know the difference between mineralisation and metal and the only way to do that is to dig every signal and be mindful that a target's volume increases as you get closer to it, but mineralised ground doesn't.
You are probably running in Difficult so most mineralisation will be filtered out, but there are still occasions where the mineralisation will still get through. If you are running it in Normal then switch to Difficult and check the hole again, that is what I do.
Good luck and may it be a good nugget.
Regards Axtyr.