The idea conveyed here is that Atma is Ekam (One) and is expressed through the matter principle. When Chaitanyam is functioning through individual matter called Sharira Trayam, then it gets the name Jivatma and when that very same Consciousness functions behinds the total matter or Prapancha Trayam, then the very same Atma is called Paramatma. Thus the same one Atma gets the name depending on the medium or Anatma through which it functions. That one Atma, I am. This is the principle of Jiva Ishwara Aikyam or Atma Ekatvam (Oneness).