code: private function readMulRk()
      {
          $length = self::getUInt2d($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 first column
          $colFirst = self::getUInt2d($recordData, 2);
  
          // offset: var; size: 2; index to last column
          $colLast = self::getUInt2d($recordData, $length - 2);
          $columns = $colLast - $colFirst + 1;
  
          // offset within record data
          $offset = 4;
  
          for ($i = 1; $i <= $columns; ++$i) {
              $columnString = Coordinate::stringFromColumnIndex($colFirst + $i);
  
              // Read cell?
              if (($this->getReadFilter() !== null) && $this->getReadFilter()->readCell($columnString, $row + 1, $this->phpSheet->getTitle())) {
                  // offset: var; size: 2; index to XF record
                  $xfIndex = self::getUInt2d($recordData, $offset);
  
                  // offset: var; size: 4; RK value
                  $numValue = self::getIEEE754(self::getInt4d($recordData, $offset + 2));
                  $cell = $this->phpSheet->getCell($columnString . ($row + 1));
                  if (!$this->readDataOnly) {
                      // add style
                      $cell->setXfIndex($this->mapCellXfIndex[$xfIndex]);
                  }
  
                  // add cell value
                  $cell->setValueExplicit($numValue, DataType::TYPE_NUMERIC);
              }
  
              $offset += 6;
          }
      }
docs: Read MULRK record
  This record represents a cell range containing RK value
  cells. All cells are located in the same row.
  
  --    "OpenOffice.org's Documentation of the Microsoft
  Excel File Format"