The depth indicator is really only calibrated to coin sized objects. Anything larger might show up more shallow and anything smaller may read deeper than actual depth. That being said, ground conditions, ground balance, trash clutter, and coin orientation may all play a roll as well as how high off the ground you swing your coil. For a coin, the depth indicator is "from the coil to the object", so unless you've got your coil in contact with the ground add whatever space between your coil and the soil to the depth reading. For what it's worth, in my area, I can't seem to get a very accurate depth reading on coins. Even with a system reset and Auto Ground balance (~91-94) the depth indicator always seems to show a deeper reading than the actual coin depth with the exception of coins on the surface, they tend to read shallow, but anything over 3" and it's a !!!! shoot. The audio response in Pro mode is a better indicator of depth in my opinion, at least once you get a little practice. I have a feeling it has to do with the highly mineralized ground conditions we have here, but that's just speculation.
