Advaita is a non dual philosophy which says there is no distinction between Jivatma and Paramatma (Brahman). There is only one soul which is Brahman.
In the Isha Upanishad or Ishavasyopanishad which is a part of Vajasaneyi samhita, there are mantras to whom the devata is Atma.
The devata of the mantras 1 to 14 and 17 is Atma. The devatas of the mantra 15 are both Paramatma and Atma. (More details about the mantras in Who is the seer of the Isha Upanishad?). Now, the devatas are said as Atma and paramatma differently.
Advaita and non dual philosophies claim no difference between atma and Paramatma. How do they interpret the devatas to the mantras of Isha Upanishad?