What is this button linked to?
CUSTOM SETUP
Open any "go to a page" button and it tells you where it currently points.

Sections
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File and page — the name of the file and which page.
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In this file / In another file — whether the target is elsewhere.
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Folder — where that file lives.
Note: For a PDF, you'll see "opens the file (no specific page)". That's normal — a PDF target opens the document rather than a numbered page.
Tip
To change the target, tap Re-capture link. It replaces what's shown.