Earlier quoted context omitted.
That's not how affirmative action works. Using your example, for most of the population, there is no detraction from their score. It only comes into effect if you have +1 and they have 0 or +1, and it becomes you with +1 and them with +2. If you had +10 and they had 0, you would stay at +10 and they would go to +2, taking the place of someone else that only had +1 and leaving you alone. For you in this case it isn't…
We're using different notation systems. I'm thinking "modifier to the dice roll", you're thinking "score". This is making it real hard to understand what you're saying. What is your understanding of how AA works?
To counter this historical disadvantage, the candidate possessing it is given additional 'points' which push them beyond the other. All other things being equal or close to equal, this becomes the tie-breaker.