refine' ⟨h₁, _⟩
α : Type u_1
inst✝ : LinearOrder α
s U V : Finset α
n : ℕ
ℬ : Finset (Finset α)
r : ℕ
h₁ : Set.Sized r ↑ℬ
h₂ : ∀ (U V : Finset α), Finset.UV.UsefulCompression U V → IsCompressed U V ℬ
⊢ IsInitSeg ℬ r
α : Type u_1
inst✝ : LinearOrder α
s U V : Finset α
n : ℕ
ℬ : Finset (Finset α)
r : ℕ
h₁ : Set.Sized r ↑ℬ
h₂ : ∀ (U V : Finset α), Finset.UV.UsefulCompression U V → IsCompressed U V ℬ
⊢ ∀ ⦃s t : Finset α⦄, s ∈ ℬ → { ofColex := t } < { ofColex := s } ∧ t.card = r → t ∈ ℬ