column-number

For an fo:table-column formatting object, it specifies the column-number of the table cells that may use properties from this fo:table-column formatting object by using the from-table-column() function. The initial value is 1 plus the column-number of the previous table-column, if there is a previous table-column, and otherwise 1.

For an fo:table-cell it specifies the number of the first column to be spanned by the table-cell. The initial value is the current column-number. For the first table-cell in a table-row, the current column number is 1. For other table-cells, the current column-number is the column-number of the previous table-cell in the row plus the number of columns spanned by that previous cell.

See http://www.w3.org/TR/xsl11/#column-number.