Number of pages of red "a book"

Hanna

The page number of the red book selling at the shop has decreased from 40 pages to 20 pages.

Is this a specified behavior?

Hanna

correction.

When copying from a light purple book to a red book, it ranged from 20 pages to 40 pages,

When copying from a red book to a thin purple book, it ranges from 40 pages to 20 pages.