From GeoGebra Manual
This tool is available only in the Spreadsheet View. There are two methods how to use it:
- Select a destination cell, then choose this tool and after that select a cell range. Count of selected cells will occur in destination cell.
- Select a cell range containing more than one cell and then choose this tool. If the cell range has multiple rows, count of selected cells each column will be inserted under this column. If the selection has only one row, count of the cells in this row will be inserted to the right of the selection. If you hold Shift when selecting the icon of this tool, the count of cells in each row of the selected area is computed.