Tony Smith sez:
Those 28 (segment) elements are mirrors of each other, and you might say that the 28 correspond to the 28-dim antisymmetric 8x8 real matrices of the Spin(8) Lie algebra that is the bivector (2-element) part of the 2^8 = 256-dimensional Clifford algebra Cl(8), which in turn is what is fundamental in my physics model, and in 16x16 = 256 IFA (which in my opinion includes the 8x8 = 64 I Ching).

More of this doggerel here.