private static function get95thIn($bill_id, $datefrom, $dateto): float
    {
        $mq_sql = 'SELECT count(delta) FROM bill_data WHERE bill_id = ?';
        $mq_sql .= ' AND timestamp > ? AND timestamp <= ?';
        $measurements = dbFetchCell($mq_sql, [$bill_id, $datefrom, $dateto]);