What is 6.28318?

What does Michael Hartl mathematician physicist say about Tau's number being 628318 and pi's number being 314159?

In The Tau Manifesto, by Michael Hartl, a mathematician and physicist, Hartl asserts that Tau should replace pi in mathematics. He and others state Tau is more perfect than pi, a perfect completion of the circle and more broadly descriptive in mathematical problems, with Tau being double of pi. This idea has not yet been accepted into mainstream mathematics; pi continues to be taught and used.Though proponents of Tau made a "Tau Day" and have produced multi-media to explain the concept, this idea is not about religions, myths, gods, etc. Pi and Tau have no mythical figures or heroic battles. The argument is simply a new mathematical idea, one which may OR may never completely be accepted into mainstream teaching and practices.