Presumably their cleanup crews consist of graffiti offenders who are put on this detail for community service.
They're saying that you'll be fined if you don't notify the city to clean it or if you don't clean it yourself.
basically, they're saying that one has no right to voluntarily have graffiti on their house.
"If you read the article it says that all you need to do is call the city and they will send someone around to clean it up."
What it doesn't say is how much the city charges for this service. Bet you it isn't free.