sort

<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
    <xsl:output method="html"  encoding="UTF-8" />
    <xsl:template match="content/collection/">
		<xsl:apply-templates>
			<xsl:sort select="@promotionid" order="descending" data-type="number" />
        </xsl:apply-templates>
    </xsl:template>
 
	<xsl:template match="content/collection/data">
        <xsl:if test="position()=1">
            <xsl:value-of select="@promotionid"/>
        </xsl:if>
    </xsl:template>
</xsl:stylesheet>