What does it mean to make the distinction between Krishna’s material qualitative incarnations and His transcendental incarnations? I am referring to Canto 1, Chapter 1, Text 17:
As the supreme controller of both the material and spiritual worlds, the Lord has different incarnations of unlimited categories. Incarnations like Brahma, Rudra, Manu, Prthu, Vyasa and so on are His material qualitative incarnations, but His incarnations like Rama, Narasimha, Varaha, Vamana, and so on are His transcendental incarnations.
Here is the meaning. Prabhupada explains that we are qualitatively one with Krishna and quantitatively different. So Brahma, Rudra, etc. are qualitative avataras in that they have realized, and act upon, their qualitative oneness with God. Therefore, they act and teach with the same divine quality as Krishna. However, they are not quantitatively God, i.e. they are not plenary or full manifestations of the Almighty.
Rama, Nrsimha, etc. are in fact God Himself. They are ‘transcendental’ in the sense that they are beyond any limitations, being fully God.