Answer: According to the book Shaar HaKavanot (The Gate of Intentions), the soul is perceived as a Partzuf (a spiritual body) that is made of ten parts (ten Sefirot), seven of which are the main Sefirot.
A soul is a Partzuf that can be either small or big, individual or general, but it is the same system, the same identical structure, that can be either global or individual, and each of the members of the ten is included in it.
The spiritual system is made of a head (Keter, Hochma, and Bina) and the seven lower Sefirot (Hesed, Gevura, Tifferet, Netzach, Hod, Yesod, and Malchut). Every lower Sefira is made of ten Sefirot, and this generates 70 spiritual roots, which the seventy major nations in the world stem from.
We can say that there are many more nations in the world, but they don’t count as major nations since they somehow spun off from and multiplied from the major nations and are now included in them but have no root of their own other than their own variation.
From the Kabbalah Lesson in Russian 10/30/16