If you're working a specific drill, BY ALL MEANS you should be adhering to the drill at first. Most of the time the drill in question is using those numbers for a relevant purpose. If, however, that purpose has anything to do with fair play for competition shooters or specific administrative scoring requirements then you can and should play with the number of loud noises a little bit.
Score is a number. In the real world, the fight starts with a clean slate... Both parties are alive and kicking. Odds are, at the end of a gunfight, one party will either A) NOT be alive and kicking; or B) be well on their way to A. Now, this can get into disparities and the like where one party may have to make up for their opponents' "higher score" due to them having more bodies alive and kicking at the get go. A criminal is NOT going to play fair, so you can leave that fair play Bravo Sierra for the birds. As far as scoring, if I'm scoring your paper target I'm looking at your kill zones (T-Slot, Heart/Lungs into spine, and Pelvic Box on some drills) and as long as no bullet holes are outside those zones I'm going to give you a thumbs up, slap on the back, a "Good Job," and go on the next target. I really don't care how many times you shoot most targets on most drills.
Why is that?