private function readClientTextbox()
    {
        // offset: 0; size: 2; recVer and recInstance

        // bit: 4-15; mask: 0xFFF0; recInstance
        $recInstance = (0xFFF0 & Xls::getUInt2d($this->data, $this->pos)) >> 4;

        $length = Xls::getInt4d($this->data, $this->pos + 4);
        $recordData = substr($this->data, $this->pos + 8, $length);

        // move stream pointer to next record
        $this->pos += 8 + $length;
    }