S -> X

Thanks to David Liu
https://stacks.math.columbia.edu/tag/02NO#comment-7806

morphisms.tex

@@ -9352,7 +9352,7 @@ \section{Ample and very ample sheaves relative to finite type morphisms}
 $$
 This morphism is an immersion as it is the composition
 $$
-S \to \mathbf{P}^n_S \times_S \mathbf{P}^{n(d - d_0)}_S
+X \to \mathbf{P}^n_S \times_S \mathbf{P}^{n(d - d_0)}_S
 \to \mathbf{P}^{(n + 1)(n(d - d_0) + 1) - 1}_S
 $$
 where the first morphism is $(j, j_{d - d_0})$ and