You should not find it perplexing that the four letters of Havaya and the upper point of the yod are the five aforementioned vessels, as the vessels are invariably called letters, and they are the mystical meaning of the five sefirot: Keter, Ḥokhma, Bina, Tiferet, and Malkhut, as stated. It is thus explicitly stated that there are vessels of Keter and Ḥokhma as well, which are alluded to by the upper point of the yod and the yod of Havaya.55The author is articulating a conceptual problem here.
The letter form representing each of the sefirot indicates a "vessel" form, as the concept of letters represents quantitative vessels for "containing" a qualitative concept. The problem is that the sefirot of Keter and Ḥokhma correspond to Atzilut and Adam Kadmon, and as the author of the Sulam explained in the previous sections, those levels have no quantitative aspect whatsoever. So, how can there be a letter representation of aspects of reality that are beyond any quantity?
In contrast, from Bina and downward, the dynamics of quantity and structure do have a place, as the author of the Sulam explained previously, so it follows that there should be letter representations of those levels. The author proceeds to solve this difficulty.