I've found a few of my 12 gold coins with my explorers (which I've used for 7 or so years now) I'm sure there are exact grid coordinates of the screen where the $1s, $2.50s, $5s, $10s and $20s would come in at, in an air test. You could do an air test yourself (if you have a coin collector friend, or find a friendly coin-store owner who would let you air test some in his shop, or whatever).
Basically, a $1 reads down a little below nickels. A $2.50 reads at about round tab. A $5 reads at about square tab (the beefier heavy kind of square tab), and so forth up the scale. But this only tells you the the "up/down" axis. It doesn't tell you the "left/right" axis. I could test mine and tell you, but it would take posting a digital pix of the screen, or whatever, to convey that.
Even if you had the exact coordinate of where they fell on the up/down, left/right axis, but as Iron patch says, it will depend. Depth, angle of tilt, proximety to trash, machine settings, etc.... can make the target vary. I do "cherry pick" when in trashy turf environments (if I want to avoid surface foil, tabs, etc.. and go for deeper potentially older coins in a very stratified turf type hunt). In those cases, I'm relying more on the up/down axis, and also computing depth of the target into it. But in no case do I think a person could mark the spot on the graph where gold coins hit in an air test, and hope to somehow go into the field, and just dig those graph coordinates, thinking they'll up their gold take. Only in air tests can you get that specific. I got a tractor knicked $10, for instance, that I bet reads slightly off from a perfect $10, because of the subtle warp and scratch. And a $1 I got, was made into a love token. For sure that one will read a little off, etc....