john g: Perhaps you are right, perhaps 10 isn't indicative of ten mines, and this despite engineers needing only to clear 10 of 'whatever' before it's no threat, which you compensate by saying they can mark the field; fine.
Only problem is, the number 10 is a finite number, it doesn't vary. Whatever it represents is what it is. If each number is 1 mine and 1 fake mine, so be it, but there are only 10 mines deadly to the units if I understand correctly. In any case, whatever the 10 represents, when one goes off, it's no longer a threat, be they fake or real.
Now, what you say would make total sense, if, if, it were not for the artillery declining the number, because artillery doesn't mark the field like engineers any better then a mine going off does. If one mine is really 1, or 5, or 10, there should be a point where those dreadful penal battalions would not go to their grave's totally fruitlessly by there being no lessening of the extent of the minefield for their going over it. So why artillery reducing a minefield and not a tank (which actually may set off more than one mine, or series of mines)?