code: private function readRk()
      {
          $length = self::getUInt2d($this->data, $this->pos + 2);
          $recordData = $this->readRecordData($this->data, $this->pos + 4, $length);
  
          // move stream pointer to next record
          $this->pos += 4 + $length;
  
          // offset: 0; size: 2; index to row
          $row = self::getUInt2d($recordData, 0);
  
          // offset: 2; size: 2; index to column
          $column = self::getUInt2d($recordData, 2);
          $columnString = Coordinate::stringFromColumnIndex($column + 1);
  
          // Read cell?
          if (($this->getReadFilter() !== null) && $this->getReadFilter()->readCell($columnString, $row + 1, $this->phpSheet->getTitle())) {
              // offset: 4; size: 2; index to XF record
              $xfIndex = self::getUInt2d($recordData, 4);
  
              // offset: 6; size: 4; RK value
              $rknum = self::getInt4d($recordData, 6);
              $numValue = self::getIEEE754($rknum);
  
              $cell = $this->phpSheet->getCell($columnString . ($row + 1));
              if (!$this->readDataOnly) {
                  // add style information
                  $cell->setXfIndex($this->mapCellXfIndex[$xfIndex]);
              }
  
              // add cell
              $cell->setValueExplicit($numValue, DataType::TYPE_NUMERIC);
          }
      }
docs: Read RK record
  This record represents a cell that contains an RK value
  (encoded integer or floating-point value). If a
  floating-point value cannot be encoded to an RK value,
  a NUMBER record will be written. This record replaces the
  record INTEGER written in BIFF2.
  
  --    "OpenOffice.org's Documentation of the Microsoft
  Excel File Format"