My 3 cents...
1) Ultimately L4S is correct, going by sound alone (what you hear not cursor) is best method
2) If you are using numbers to learn, that's fine, but they can become a set of crutches you never want to get off of.
While you are using #'s, going to an open quickmask screen will work most the time, but if its a case where a silver coin is co-located with iron trash, quickmask may lead you to believe this is solidly an iron object and what you heard was a false (particularly if you are running with high trash on). Which in reality is not the case in this instance. Which goes back to listening.
A lot of the times you get these falses because the very edge of your detector's profile of sensitivity is just barely running across the edge of iron junk. pinpoint and see if where you hear 12-43 is where the object actually is. Chances are if pinpoint is off by an inch or more from where you hear it, it's an iron object.
3) Using sound (not looking at #'s) and pinpointing give a good approach. If what you pinpoint (like said above) is way off from where you hear the high tone in your sweep, you likely are falsing off of iron. This does not work in high trash areas where you may just have to go off of sound and dig where you here the sound... Use the machine enough and you'll become accustomed to how iron false sounds, but a lot of times I still dig those hoping I am wrong...
Another possibility is you are running with sensitivity too high...