How to set on Visible pages?

Hi,

I have key in on the visible page as : 1,3,6,9,23…….

and also tried 1-4, 3,5 …..

Nothing seems to work. It only show the first page visible.

Kindly advise what is the right way to put in so that the pages I wanted is visible.

https://wordpress.org/plugins/pdf-light-viewer/