One reason I do not put any reliance on Depth indicators is that as a rule of thumb, most anything you find is on the surface to at or about 3-4 inches deep.
The other reason is, unless your coil is scrubbing the ground, you are at or about an inch or two above the ground. What may detect at 2 inches of air may not detect the same as 2 inches of air and 2 inches of ground and so on.
Multiples of targets under the coil can also goof up depth indicators as well as target identity. Sometimes you can raise a concentric (round) coil higher above the ground to reduce the number of targets that are all at once interrupting the coil field. The coil field of a concentric coil is like the shape of an upside down cone and so naturally, the higher up it is, the less area of air and ground it detects. Sometimes, this can be used to an advantage in working trashed out areas or with multiples of targets, simply by process of elimination, digging the shallowest down towards deepest. It is possible to have a trash target above and or in close proximity to a good target and is why there are those of us who will dig all targets to recheck for second target and so on. If a person does not want to spend the time and put in the work to learn to detect by sound, Tone and display detectors will get you in the ball park but as I've said, they can also be fooled and in some ways, be just as frustrating.
I have found pocket dumps that made my 505 go bonkers but when I set it to all metal to pin point and then began digging each sound, one by one, I got all the coins dumped but granted, I had no idea what coin they would be until I saw them. If I had placed all my confidence in that a junk target is supposed to read as an inconsistent unrepeatable tone and displayed target, I would have moved on thinking I had detected junk. I know people like to defend these Tone and Display machines all the way to their graves but they are not perfect. Yes, I will give in that for beginners, they are initially not as frustrating to operate but that is because the operator is not having to so much understand what the machine is doing and in blind trust, has to accept what it's telling them.
I hope you don't get me wrong, I like my 505 and it has been a very fun machine. I don't regret buying it at all and feel if BH coin/relic machines are not nipping at the heels of the more Name Brand high dollar units, they are out doing them.