How to fix "A non-numeric value encountered" error?

Question

PHP

When displaying news on the page, it swears at this code, or rather at the line:

return $this->conn->query("SELECT * FROM `news` ORDER BY `created_at` DESC LIMIT ".abs($page*$per_page).",".$per_page." ")->fetch_assoc_array();

public function getListNews($page,$per_page = 3){
        global $func;
        $page = $func->clearQuery($this->conn,$page-1);
        return $this->conn->query("SELECT * FROM `news` ORDER BY `created_at` DESC LIMIT ".abs($page*$per_page).",".$per_page." ")->fetch_assoc_array();
    }

I also use it on the page.

$page = 1;
if(isset($_GET["page"])) $page = (int)$_GET["page"];

$list = $news->getListNews($page, 9);

$count = intval(($news->getCountNews() - 1) / 9) + 1;

if(count($list) == 0){
    $page = $count;
    $list = $news->getListNews($page, 9);
    if(count($list) == 0){
        $out = "Новости не найдены!";
    }
}