Warning 3.5.6.7. Let $X$ be a Kan complex. We have now assigned two different meanings to the notation $\pi _{\leq 1}(X)$:

The fundamental groupoid of $X$ (Definition 1.4.6.12), which is a category.

The fundamental $1$-groupoid of $X$ (Notation 3.5.6.6), which is a simplicial set.

However, the danger of confusion is slight: by virtue of Example 3.5.6.3, the fundamental $1$-groupoid of $X$ is isomorphic to the nerve of the fundamental groupoid of $X$.