It's super important for affirmations to be believable. If you want to increase your income to $10,000 a month, and are currently making $1,500 a month, saying "I have an income of $10,000" is probably not going to feel very believable.
It would probably feel more believable to say something like, "I am open to making money in ways that surprise and delight me."
Or, "Money comes to me in many different ways."
