event.cellColumnId : Is there a mistake in the documentation ?

Hi,
I’m searching how can I get a column Id when user clicks on a cell in a $w table.
I found “event.cellColumnId” in onCellSelected function.
The documentation says that it returns the Id of the selected cell’s column.
But when I check it, it returns the “label” of selected cell’s column.

Am I wrong ?

Thank you