In the explanation you can read:
Note we use “andThen” here – f andThen g means f(g(x)). There’s another combinator “compose” – f compose g means g(f(x)).

I think it should be the other way around:
Note we use “andThen” here – f andThen g means g(f(x)). There’s another combinator “compose” – f compose g means f(g(x)).