Hi!
Do you mean on the live results list? On the results page I am seeing 15 results, for example: http://scopus.fair-agenceweb.fr/?s=mat
For 15 items per page, you need to adjust the results width and the column count under the Theme Options -> Isotopic layout panel: https://i.imgur.com/2WVXRkz.png
The number of items per page is calculated by the width and the rows count, as it depends on the search width as well, where it is placed. So by lowering the result width you will get more columns, and increasing the rows will add new rows as well.
