XSLT » xsl:number » format="{ string }"

The optional format attribute is set to an Attribute Value Template that dictates the output format for the number. You can use any the following choices:

FormatOutput Sequence
11 1 2 3 4 ... 10 11 12 ...
01 01 02 03 04 ... 10 11 12 ...
a a b c ... z aa ab ac ...
A A B C ... Z AA AB AC ...
i i ii iii iv v vi vii viii ix x ...
I I II II IV V VI VII VIII IX X ...