Hi Mahesh,
You need to create a separate additional group for the ArrivalEventdate element.
Please see below.
XSLT fragment
<Arrival>
<EventCount>
<xsl:copy-of select="ArrivalEventCount"/>
</EventCount>
<xsl:for-each-group group-by="ArrivalEventdate" select="/Booking/value">
<Line_No>
<xsl:copy-of select="position()"/>
</Line_No>
<xsl:copy-of select="ArrivalEventdate"/>
<xsl:copy-of select="ArrivalEventDetail"/>
</xsl:for-each-group>
</Arrival>