It is sometimes called the 'for-itself' as if self-reference were immediately understood, but you can conduct the thought experiment of imagining that your entire subjective experience belongs as a small reduct to a larger subjectivity structurally inaccessible to what is taken as yours. The fact that this is possible shows a latent knowing that you don't know who or what this all is 'for'. Just as it's possible to 'see', with some training, the blind-spot in your optical organ, so you can become 'aware' of the unconscious spot in the heart of your consciousness.