How does proportional-column-width work in xsl fo

How does proportional-column-width work? In the below example, what would 1 or 3.5 or 2 mean? Should these total to 10 which would make it 100%? or should I be specifying percentages instead?

``````<fo:table-column column-width="proportional-column-width(1)"/>
<fo:table-column column-width="proportional-column-width(3.5)"/>
<fo:table-column column-width="proportional-column-width(.8)"/>
<fo:table-column column-width="proportional-column-width(2)"/>
<fo:table-column column-width="proportional-column-width(1)"/>
<fo:table-column column-width="proportional-column-width(2)"/>
<fo:table-column column-width="proportional-column-width(1.5)"/>``````
Gertone (Geert Bormans)

It is "proportional" compared to the other columns
the fourth column will have twice the width of the fifth column
as 2 to 1 in the proportional width

basically you can add all the proportional widths together, divide 100 by that total and for each column multiply by the proportional width value to get the % width