The clue part is not a clue, it's an essential part of the information (otherwise how should anyone figure out what even is the task without looking at the test cases?). But then this paragraph is pretty useless at explaining the task, so it really should be rewritten. e.g:

They are all connected to the golden ratio when the length and height represent the golden ratio, ie/ length = 13 and height = 8.

How is 13 / 8 the golden ratio (1.618033...)?

To calculate this you need to find the validator that matches the hash mod total stake of all validators.

Can the description be more useless than this?

The hash is 4 bytes while the array consists of 2 bytes of numbers, so what does it mean to mod them? (Doing it the obvious way doesn't lead to anything.) What does it mean for a validator to "match"? Why is chosenValidator("21e66e37e", [25,5,20,25,20,5]) equal to 4 if both 2 and 4 are 20? There are so many questions.