The SUBTRACT statement has the form
SUBTRACT exp1,exp2;var
and places exp2-exp1 in var. If var is omitted, exp2 must be a variable, and recieves the result of the subtraction.
The comma may be replaced by &'FROM', and the semicolon by &'GIVING'.
Note that SUB is an abbreviation for SUBROUTINE, not SUBTRACT.
Use of a colon instead of a comma interchanges the roles of exp1 and exp2.