May have learned something ond VID numbers and depth of target

[Michaeltime]

I got new TDK WR700 wireless headphones today. In testing them out I wanted to see how far from a penny I could hear the sound. As I went further away then normal the VID numbers and what it was changed to many different readings. I got foil, iron, pulltabs and other readings all the way to a whisper and no target Id. I am guessing I may have to look on target id as an insentive to dig, and bad target ids as something I have to check for depth.
M6 Mike
I think I got as far as 12 plus inches from the penny and seen nothing on the screen but could hear the penny and further just a whisper each pass over it.
I been detecting a long time and never give it a thought if it said foil or iron I moved on never checking the depth of target. I started back in 1973 detecting off and on.