Maximal cross-ratio degree for 8 points in ${\mathbb{P}}^1$

The cross-ratio degree problem asks for the number of configurations of $n$ points in ${\mathbb{P}}^1$ that satisfy $n-3$ specified cross-ratio conditions. It is known that the maximal cross-ratio degree for 8 points is at least 4. In this paper, we will see that the maximal cross-ratio degree for 8 points in ${\mathbb{P}}^1$ is equal to 4.