"I think, therefore I am"-René Descartes

Since the last time, it was said that the quote "I think, therefore I am" meant that it is the purpose to use knowledge to prove existence in the world in that particular self-subject. Now that it is known what it means,  to prove existence, the purpose is to perceive you exist, therefore you exist. In contrary, the act of perceiving is an irrefutable truth which means it's dubitable. In other words, the quote means that since Descartes is thinking, therefore is he is (existent).