This is interesting ...
The value is zero because at the point in time, according to XSLT 1.0
Section 7.7 the <note> element isn't being processed and there are no
preceding notes, so there is nothing to count.
But section 7.7.1 states that integers being processed are
greater than zero.
So, I'm guessing it is incumbent on the stylesheet writer
never to be in
the position of getting a zero value when using <xsl:number>. But it
doesn't say that explicitly in the Recommendation.
Can anyone on the committee comment on this? Are users of
<xsl:number>
required to use it only in situations where a positive number
is being returned?
Erratum E23 fixes this contradiction in the spec, specifying that an
empty list is returned in this situation, not a list of length one
containing the number zero.
http://www.w3.org/1999/11/REC-xslt-19991116-errata/
Michael Kay
XSL-List info and archive: http://www.mulberrytech.com/xsl/xsl-list