What does it mean by $x \not\in A \smallsetminus B$ when $B \subset A$?

Question

Let $B \subset A$. Then by set definition $x \not \in A \smallsetminus B$ implies $x \not \in A$ and $x \in B$. But to me this is absurd. What is happening when $x \not \in A \smallsetminus B$ when $B \subset A$? Thanks.

Answer 1

$x \in A \setminus B$ means $x \in A$ and $x \not\in B$. So $x \not\in A \setminus B$ is the negation of that: $x \not \in A$ or $x \in B$.