What you'll do: check the structure Bookbndr detected and fix any heading that's been put in the wrong place.
When Bookbndr scans your document it automatically labels every heading with a zone — chapter, part, section, front, back or excluded. It's usually right, but it's worth a quick look on the Chapters step.

Read the labels
Each row is a heading from your document, with a colored tag showing its zone. A banner at the top summarizes what was auto-detected, for example "Auto-detected: 2 parts, 3 sections, 1 front, 1 back."
Change a heading's zone
- Find the heading you want to change.
- Click Move to… on its row.
- Pick the correct zone — Chapter, Part, Section or Excluded.

The tag updates immediately. If you change your mind, click undo on the tag to go back to the automatic guess.
Merge a heading into the previous chapter
Sometimes a Heading 1 is really part of the chapter before it (say, a section break that you styled as a big heading). On that heading's Move to… menu, choose Merge into [previous chapter] to fold it in. A Merged badge appears, with its own undo.
Nothing showing up?
If the list says "No headings found", your chapter titles aren't styled as Word headings. In Word, apply Heading 1 to each chapter title, then come back and press ↻ Re-scan document. Not sure how? See Use Word styles to structure your book.
→ Background: Chapters, parts & sections.