add this snippet code to yourtheme/functions.php or snippets code plugin

 add_filter('op_get_login_cashdrawer_data',function($session_response_data){
    
    
    $session_response_data['setting']['openpos_auto_logoff']=array('screen_time' => 5,'popup_wait_time' => 10); // warning appear when have no action on screen in 5 minutes, and the warning count down is 10 seconds
   
   
    return $session_response_data;
 },1001,1);