Hi Edward,
I stumbled into your post so I thought I would add by opinion if you don't mind.
Now, from a technical standpoint, a coin can read higher than normal as the result of the ground conditions. The analysis is basically done using math means that adds the ground signal to the target signal. As the target signal becomes weaker and weaker, the ground signal begins to dominate, thus the higher reading. George Payne wrote about this quite a while back. His explanation can be found on the Treasure Baron Forum. Here is the link to what George Payne wrote if you are interested.
http://jb-ms.com/Baron/IDmeters.html
BTW, if you are fairly new to coin hunting and do not know who George Payne is, well, if you like TID, audio ID, notch, blanking, ground balance in general, or simply the transition to the VLF, he is the guy to thank. Yep, he designed the first VLF, the first, motion discriminator, the first TID, the first audio ID, the first notch feature and a few others I can't think of at the moment. Not bad for one guy,huh?
Now, if there are few hotrocks in your area, I would recommend you turn on the +95. Years ago, when I was using another Whites unit, I found that even turning on the highest 3 or 4 highest negative numbers (maybe -96 through -92 also) would also increase the number of coin finds without causing me to dig much trash. So, this is something else to think about. I used to call this sort of cheating but after finding out just how the distortion occurs, I call it distortion compensating. It is the same thing but it does make some people feel better when they try it.
Reg