Aloha e @Sherry, it depends if you are describing a quantity vs. a numbered position; one is a special word ma ka ʻōlelo hawaiʻi and is a bit irregular compared to the other numbers. If you remember from previous lessons, "hoʻokahi" was used before the word being quantified as in "hoʻokahi noho; ʻelua noho" - one chair, two chairs. When placed after, as in "ka noho ʻekahi, ka noho ʻelua" the meaning is then "the first chair (or ʻchair number oneʻ)" and "the second chair (or chair number 2).
So in the sentence here, "hola ʻekahi" is really saying "the first hour" or "hour #1". Hope this helps.