The Member listing element is used within the Members directory template. The template is used to render members within the members page.
In order to increase the number of members rendered, you will need to add the following code within the functions.php file of your child theme:
function bp_member_listings_per_page( $members ) {
$members['per_page'] = 24;
return $members;
}
add_filter( 'bp_after_has_members_parse_args', 'bp_members_listings_per_page' );
You may alter the value in place to that of your preference