Hi,
Just to say that in the documentation for gallery acf type at the end of code exemple, the “Create a WP gallery” part isn’t complete:
http://www.advancedcustomfields.com/resources/gallery/
Thank you for this great plugin 
Hi,
The documentation page seem you reference appears to be complete to me. I’m not the writer or maintainer of the documentation but the section you mention I think is just supposed to be an example of how the gallery field might be used it use a standard WP gallery shortcode and I think that you are supposed to see the WordPress Codex page on the galley shortcode tag for more information. https://codex.wordpress.org/Gallery_Shortcode
Can you elaborate on what you feel is missing?