I agree with HighVDI. If you do not hunt multi-tone (50 tones), then setting one of your tone bins, in the 11-13 zone, as high tone, it will clue you in better (set that tone bin the same as the tone you use for your other coins, is an option). I don't use 5 tones, never have on this unit -- but I know this is a strategy that some use, when they don't want to miss nickels.
Few things. If you dig 11/12 signals, you will dig beaver tails. A beaver tail hitting 11/12, will sound similar to a deep Buff or V-nickel, because being a smaller target, it sounds deeper, and thus will fool you into thinking "deep nickel." But that's just part of the game. I rarely hit nickels that bounce to 14; maybe a very rare 14 bounce, but any consistent 13-14 bouncing will be a rectangular tab, or can slaw, or lead, or whatever (OR, a gold ring, LOL). A war nickel is also a possibility in that range just above 13. However, a shallow nickel is often a solid 13, similar to an air test. The deeper they get, and the older they get, you will see more 12s in the mix (or even 11s). I have occasionally dug a Jefferson nickel that is a solid 12, even in an air test, but usually they are 13. Bottom line though is, if you are targeting nickels, you WILL dig a good number of beaver tails (11-12), small rectangular tabs (13-14), .22 shells (11-12), can slaw, lead chunks, etc. As you know, that's just "the name of the game" when digging nickels.
Last thing -- my whole post is focused on VDI, and obviously, if you are "VDI-focused," you are "not completely doing it right," IMO. SOUND is the name of the game, with Minelab machines. Those numbers, PLUS a good, mellow "round" sound, is also a good part of the mix, when trying to identify nickels. If I hit a target that is a solid 13 from one angle, and I turn 90 degrees and its a pretty consistent 12, or 14, that suggests NOT a round target (and you hear that same hint in the tones, if you are running 50 tones). The machine is seeing the "short axis" and "long axis" of the target, if it is, say, a rectangular tab, and that's the reason turning 90 degrees will give you a slightly different VDI and tone.
These subtleties are what will eventually, through experience, allow you to dig more nickels, and less junk. It is NOT foolproof, and orientation of target in the dirt, and any nearby targets, will affect this, of course. But using your ears will get you a lot better in terms of the "trash to treasure" ratio.
Steve