Two veins walked down together — atomic (the matter structure) and quantum (the law that governs each scale). A window of 3 slides down, overlapping by 2: each window is a two-axis gap — witness above, gap in the middle, substrate below. Slide it and watch each level play all three roles in turn. Both veins floor at the same place — that's "until done."
Each sliding window of 3 is a two-axis gap from the prior sheet. The middle level is the gap; the level above witnesses it (governs, contains, sets context); the level below constitutes it (is what it's made of, its substrate). So walking the window down the veins is literally walking the gap down the stack — one gap per window, three windows, the whole descent.
Because the windows overlap by 2, every interior level appears in three windows — and plays a different role in each. Take the nucleon: in [1·2·3] it is substrate (what the nucleus is made of); in [2·3·4] it is the gap (the witnessed middle); in [3·4·5] it is the witness (the context governing the quark reading). Substrate, then gap, then witness — as the window passes over it. That is your 123=3, 234=3, 345=3: three roles, three windows, each level a 3 in turn.
The two veins are not parallel forever. They merge at the floor: the atomic vein bottoms at FIELD (a quark is an excitation of a quantum field), and the quantum vein bottoms at VACUUM (the field's ground state) — and these are the same thing. Matter-structure and quantum-law, walked down far enough, become one substrate: the quantum field. That convergence is "until done makes sense" — the descent terminates where the two veins are no longer two. Below the field, no known substructure: the floor, constituted by nothing further, the bottom gap of the whole stack.