Although the Sefirot appear in the form of likenesses, even so, the form seen is not like a physical form. What is seen is something that is understood as if one saw that form in the lower world. This is called the vision of the soul, whose vision is not like the vision of the body. Accordingly, the subjects of the prophetic vision do not necessarily appear in the same way as the corresponding physical objects would appear to the physical eye.
What is seen by the soul is a shining light that is understood as a circle (igul) if what is seen is “circular”, or as a straight line (yosher) if what is seen in the vision is “straight”. The same applies to all the other forms or images seen by the soul: it is not that the actual physical form is seen. Even the spiritual form that is seen is not of the intrinsic essence of the Sefirot themselves, but only the way they appear through Malchut, which shows these powers in this way.