Show/Hide index page number -> what's the meaning?

[dibu]

Hi,
if I want to register a new book, there is a field, named "Num. page index" with the description: "Show/Hide index page number". I don't know what's the meaning of it. Show/Hide-format normally is a boolean, but it seems to be a number. For example: a book with 189 pages and index at page 190. Is it meant to insert "190"?
best regards
Dieter

[federica]

Hi dibu,
the "Num. page index" is useful when you insert to the book only a chapter of a book. The "Num. page index" is the page number index of that chapter.