Part 2: …whether by receiving from his back parts or receiving from his front… These are all the different states of Nukva. She may be either Back-to-Back or Face-to-Face, and this in one of two ways: …be it from the chest and below or the chest and above. All these are different ways already prepared by Zeir Anpin whereby Nukva ascends or descends depending on the deeds of the lower creations, as the proposition goes on to say.
These are all different states in which she may ascend or descend, depending on the deeds of the lower creations. Everything has its own defined order. Despite the vast multitude of deeds, all come under a finite number of categories which the Supreme Thought prepared in advance to suffice for everything that is destined to come about. (These three states are the general categories that include all possible relationships between Zeir Anpin and Nukva as determined by men’s deeds.)