Complex sentence: GN-z11 is observed as it existed 13.4 billion years ago, just 400 million years after the Big Bang, as a result, GN-z11's distance is widely (and mistakenly) reported as 13.4 billion light years.
Split into simpler sentences: GN-z11 is observed as it existed 13.4 billion years ago, just 400 million years after the Big Bang. Its distance is therefore widely (and mistakenly) reported as 13.4 billion light years.