position() misunderstanding

=== test.xml ===
<?xml version="1.0" encoding="UTF-8"?>

<Catalog>
	<Book>
		<Title>Dune</Title>
		<Authors>Frank Herbert</Authors>
	</Book>
	<Book>
		<Title>The Stars My Destination</Title>
		<Authors>Alfred Bester</Authors>
	</Book>
	<Book>
		<Title>SLAN</Title>
		<Authors>A. E. Van Vogt</Authors>
	</Book>
</Catalog>

<xsl:template match="/">
	<content>
	<xsl:apply-templates/>
	</content>
</xsl:template>

<xsl:template match="Book" >
	<Book>
		<xsl:value-of select="Title"/>
		[<xsl:value-of select="position()"/>]
	</Book>
</xsl:template>
</xsl:stylesheet>

=== testresults.xml ====
<?xml version="1.0" encoding="UTF-8"?>
<content>
	<Book>Dune
		[2]
	</Book>
	<Book>The Stars My Destination
		[4]
	</Book>
	<Book>SLAN
		[6]
	</Book>
</content>