The second axiom of Objectivism is that consciousness also exists as the process of perceiving existence. Consciousness is consciousness of existence. Without a reality, there would be nothing to be conscious of. While you can't have consciousness without existence, you can have existence without consciousness. This is the primacy of existence.
Facts exist independently of any particular consciousness.
They are what they are, which is to say, they are objective. The primacy of consciousness denies this view. It states that consciousness creates reality. Reality is merely a by-product of a certain mental process. In their view, reality is not objective.