This template simply produces the "minus" (U+2212) character. Use {{subst:User:AlanM1/Template/M}} in place of the minus and it will be replaced when saved. Note that this does not work in other templates—the substitution happens upon transclusion—so you have to put the text in the sandbox, save it, then edit it again to copy and paste the text that now contains the '−' character :(
