The example uses (n + 3) in a list of five items. Start counting from the 3rd item - ok, the visualization[1] shows us counting from the 3rd-from-last, so now I'm already confused. And then we count "until the end", which actually shows us counting back toward the beginning[2]. And we end up with 3 items. Are they the last 3? The first 3? I can't tell. The author should have chosen a number that didn't sit at the halfway point of the total number of items.
The description makes it sound like we start at 5 -> 4 -> 3, then select 3 items, so we select 3 -> 4 -> 5. But that's a tautology. I think what it means is that we start at 1 -> 2 -> 3, and select 3 -> 4 -> 5... is that correct?
[1] https://ishadeed.com/assets/css-has-nth-last-child/nth-last-... [2] https://ishadeed.com/assets/css-has-nth-last-child/nth-last-...