The first step begins with finding out what the variables actually contain. Taking your word for it that the variables are actually numeric, the only way that parentheses print is because the variables are printed with a format. So you have to remove the format and print a few actual values to get some idea of what the variables contain. Luckily, that is easy:
proc print data=have (obs=20);
var column1 column2;
format column1 column2;
run;
After that, it's possible that you will have enough information to perform the subtraction.