To be precise the "higher" order state where opposite polarities fully coincide should be represented by the dimension 0.

So here opposite polarities which in the dualistic language of separation = 2 (i.e. 1 + 1), here in nondual terms = 0 (i.e. 1 - 1).

Remarkably - even in analytic terms - any number expressed with respect to the dimension of 0 = 1.

So 1⁰ = 1.

In true complementary fashion likewise 0 ¹ = 0. So even in analytic mathematical terms there are close quantitative/qualitative connections as between 1 and 0.

Likewise in dynamic holistic terms, non-dimensional reality (0) represents the state of unity (1) where we have close quantitative/qualitative connections as between form (1) and emptiness (0).

So strictly - of course - in nondual terms we do not have "higher" order dimensions.
However when we wish to express - in reduced dualistic fashion - the corresponding structures which - in dynamic mode - are appropriate to the non-dimensional spiritual states it is then appropriate to express dimensions in "higher" order dualistic terms. We then have 2, 4 and 8 dimensions respectively relating to opposite polarities in horizontal (2), horizontal and vertical (4) and finally horizontal vertical and diagonal terms (8) respectively.

When these are expressed - in reduced linear (i.e. one-dimensional terms) we generate the appropriate dynamic structures appropriate - in dualistic language - to the "higher" order dimensions and - equally from a nondual perspective - the structures appropriate to the non-dimensional spiritual states.

The very essence of this approach is that there is no elevation of form over emptiness (or emptiness over form) for in the dynamics of experience they are necessarily interdependent.