As is known, light cannot be contained without a vessel, and you are also aware that these five levels of opacity in the partition come from the five levels of opacity in the fourth level. That is, before the constriction (tzimtzum), there were five vessels in the fourth level that enclothed the ten sefirot, Keter, Ḥokhma, Bina, Tiferet, and Malkhut, as stated in section #18# above. After the first constriction, they were incorporated into the five levels of the partition, so that through the returning light that it raises, they return to being five vessels for the ten sefirot, Keter, Ḥokhma, Bina, Tiferet, and Malkhut, formed from the returning light, replacing the five vessels that were in the fourth level itself prior to the constriction.