Reduction according to the Ari

Hello,
In your book ‘No Man Has Dominion Over His Spirit’, page 93, there is a circle with a dot in its center that, according to the Ari, describes the end of the process of reduction.
Question: Is the circle a sphere? What is the envelope? What is beyond the envelope? What is the point at the center of the circle?
Thanks in advance,
Ephraim