You can thus see how five shiurei koma (literally, “dimensions of height”) of the ten sefirot emerge through five types of fusion through collision against the partition, which are determined by the five levels of opacity (ovyut) within the partition. I will now inform you of the reason for this.
Dimensions of Height and How the Ten Sefirot Emerge
Petichah LeChokhmat HaKabbalah 22:1