It's the assignment part; it says where the result should go. In this case, back to the "COBOL" variable. But, it's optional if you're assigning back to the source: ADD 1 TO COBOL means the same thing as ADD 1 TO COBOL GIVING COBOL. But, you can also do ADD 1 TO COBOL GIVING FOOBAR to assign it somewhere else.

(Yes, I just spent the last 10 minutes reading the COBOL pages on Wikipedia and Wikibooks.)