I don't have the MX7, but I do own the MX Sport (supposed to be the same machine with waterproofing).
The MX7 seems (to me anyway) to be a fairly popular machine. Lots of people using them in the various FB groups - from what I've seen anyway.
You might consider asking your question(s) on one of those groups.
Silverslingers has a YouTube channel. Last I knew Dominique was using an MX7. She is very successful and I've witnessed her helping a number of people (who had questions) on FB.
There is also the option of going to Whites forums. Google it - I can't give the link (board rules).
It seems to me that most detecting videos show the targets that seem likely to be good - hence the steady numbers.
It is best if you make it a habit of listening to the tones vs watching the numbers.
You might want to reset your machine - back to the factory settings.
Ground balance it over "clean" dirt (no targets). Press/hold tracking button while bobbing the coil up and down. When the sound is the same (up/down) the machine is ground balanced.
My experience (MX Sport) is that the numbers are steady - varying by a number or two - when the target is "clean." By that I mean it isn't affected by nearby trash, or other targets. I have seen numbers vary quite a bit when there is something masking a good target - like trash next to a good target.
Sweep potential targets from several directions - (move around the target so the coil approaches it from different angles). For me, if the tone stays good and the numbers are fairly steady - dig. I tend to hunt really trashy areas and it is very common for me to dig both trash and good targets out of the same hole. The trash often alters the numbers.
Use pinpoint to see how large/small the potential target is. If the target is larger than a coin, it likely isn't a coin (or there is trash, other targets, nearby).
Larger rusty metal can sound like a good target. It can read like a good target too. One trick to avoid digging rusty metal is using the iron audio feature - it lets you choose to hear the items that are discriminated out. You can select a percentage (volume wise) so the discriminated items aren't as loud as the accepted items (I tend to run iron audio at 40%). Sweep the coil back so the target is just off the front of the coil - a ferrous item will give an iron grunt as the coil moves from over the target. A non-ferrous target will still sound good. (This works great with bottle caps too). Using the pinpoint function to size the potential target helps too - if the target is large, you know it isn't a coin/ring.
Flattened aluminum cans often sound great and they can show up with good numbers too (silver dime/quarter). Check the target size with the pinpoint function - a can is way larger than a coin. Another trick is to raise the coil while you're swinging it over the target. If you're still getting a great tone/number and the coil is 10 inches above the ground - it's almost certainly a flattened aluminum can. Flattened aluminum cans typically read (depth) like they're on top of the soil, or just barely below - you can also check a target by using your hand-held pinpointer; if it doesn't give a signal the target is deeper than it shows on your MX7 (and very likely a flattened aluminum can).
Don't turn the sensitivity way up. The MX Sport is a very sensitive machine. Too high of a sensitivity setting will impair your ability to find good targets. Run sensitivity so the machine is stable (mine is usually around 6 or 7).
Bury a few coins in clean ground. Then practice swinging the coil over them. Pay close attention to the tones - let the tone alert you to a potential target. Then look at the numbers - my guess is that you'll find the numbers to be steady and repeatable from multiple directions. Practice sizing the target using the pinpoint function.
Trash is part of the game. You're going to dig trash - it is what it is. A couple of days ago I hunted one of my usual spots (MX Sport) - tons and tons of trash (it used to be a auto repair garage/junk yard). There are car parts all over the place - small, large, and everything in between. I dug 3 pouches full of trash in a couple of hours - most of it coin sized copper/brass/lead etc.. I also dug 2 silver quarters and 3 silver dimes (nothing older than 1941). I dug everything that gave me a repeatable good tone - even if the numbers weren't quite right. Only one good target (silver quarter) was by itself in the hole. All the other good targets had trash in the hole too.
