The staircase of f is governed by T(k) = max{m : h(m) ≤ k}: f = k exactly on [2T(k−1)+2, 2T(k)+1], with certified values T(1)=1, T(2)=3, T(3)=6 and T(4) ≥ 13. The 13-element class set {1,2,3,4,5,6,7,8,9,10,12,13,15} has no dissociated 5-subset (verified exhaustively over all 1287 5-subsets), showing extremal class sets stop being initial intervals at k=4: intervals only give T(4) ≥ 12, capped by the Conway–Guy-type set {6,9,11,12,13} ⊂ [1..13] with distinct subset sums.