What does $2|x_1=u$ mean here?

Question

In the Wikipedia article

https://en.wikipedia.org/wiki/Wieferich_prime

under the section

"Connection with other equations"

I came across the equation $$2|x_1=u$$ The explanation seems to indicate that $2|x_1$ is the valuation of the lowest solution with respect to $2$.

Did I understand this correctly ?

Answer 1

It means that $2$ divides $x_1$ (which is what $2 \mid x_1$ means) and that $x_1 = u$. This is not a common notation.

Note to others checking later: I've edited the wikipedia article to not have this notation anymore.