In SO, when I view unanswered questions list, I see that some questions are repeated. For example, the question I saw on page 3 is the same question shown on page 4.
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That's because between the time you requested page 3 and the time you requested page 4, one or more new questions were asked (or for other reasons appeared on top of the list).
Assuming you view 50 questions per page, page 1 will contain the first 50 questions, page 2 questions 51-100, and so on. What counts is the questions available at the very time you request the question list. And if a new question appears at the top (i.e. it's a new question 1), then what used to be question 50 (on page 1) is now question 51, so it's on page 2.