Let P(i, j) be the control points of the quadratic Bézier surface patches, C(P0, P1, P2, t) represents a quadratic Bézier curve with control points P0, P1 and P2 with parameter t and S(u, v) the quadratic Bézier surface patch equation. We are trying to explains to you that

S(u, 0.7) = C( C(P(0,0), P(0, 1), P(0,2), 0.7) , C(P(1,0), P(1, 1), P(1,2), 0.7) , C(P(2,0), P(2, 1), P(2,2), 0.7) , u).