An error in Figure 13.13 of Bishop's PRML?

This figure comes from Chapter 13 Sequential Data in Bishop's Pattern Recognition and Machine Learning (PRML).

I am not sure whether there is an error that it seems like the $$ p(\mathbf{x}_n|z_{n+1,k}), k=1,2,3 $$ in Figure 13.13 should be

$$ p(\mathbf{x}_{n+1}|z_{n+1,k}), k=1,2,3 \,. $$

I am wondering can anyone who has read this book give me some advice?