If a chapter contains a section start, the section page numbering remains in effect throughout the book until QuarkXPress encounters a new section start. For example, when the first chapter in a book is a section with a page number prefix of “A” all the pages in following chapters will have the “A” prefix until QuarkXPress encounters a new section. In this example, the second chapter might be a new section with a “B” prefix.

You can add, change, and delete sections in book chapters at any time (Page > Section). If you remove all the sections from all the chapters in a book, the book will revert to sequential page numbering.