Xpath Expression Help

In the attached stylesheet I need to transform the XML to add various counters the trailer elements.  An example is the CTT_347 element that needs to contain the count of the IT1_01 nodes within the same SG0.  My code worked well until I had two SG0 nodes in the file.  The second CTT_347 node gets the total of all the IT1_01 nodes from all the previous SG0 nodes as well as the current one which is wrong.

Is it possible with a single Xpath expression to get a count of only the IT1_01 nodes within the current SG0 node?

   <xsl:template name="HL_segments">
      <xsl:choose>
         <xsl:when test="name() = 'CTT' ">
            <xsl:element name="CTT">
               <xsl:element name="idCTT">CTT</xsl:element>
               <xsl:element name="CTT_354">
                  <xsl:value-of select="count(preceding::IT1_01)"/>
               </xsl:element>
            </xsl:element>
         </xsl:when>


<?xml version="1.0" encoding="ISO-8859-1"?>
<ACTIS>
   <ISA>
   </ISA>
   <GS>
   </GS>
   <SG0>
      <ST>
         <idST/>
         <ST_143>810</ST_143>
         <ST_329>0001</ST_329>
      </ST>
      <BIG>
      </BIG>
      <IT1_01>
      </IT1_01>
      <IT1_01>
      </IT1_01>
      <IT1_01>
      </IT1_01>
      <IT1_01>
      </IT1_01>
      <CTT>
         <idCTT/>
         <CTT_354/>
         <CTT_347/>
         <CTT_81/>
         <CTT_355_01/>
         <CTT_183/>
         <CTT_355_02/>
         <CTT_352/>
      </CTT>
      <SE>
      </SE>
   </SG0>
   <SG0>
      <ST>
         <idST/>
         <ST_143>810</ST_143>
         <ST_329>0002</ST_329>      
      </ST>
      <BIG>
      </BIG>
      <IT1_01>
      </IT1_01>
      <IT1_01>
      </IT1_01>
      <IT1_01>
      </IT1_01>
      <CTT>
         <idCTT/>
         <CTT_354/>
         <CTT_347/>
         <CTT_81/>
         <CTT_355_01/>
         <CTT_183/>
         <CTT_355_02/>
         <CTT_352/>
      </CTT>
      <SE>
      </SE>
   </SG0>  
   <GE>
   </GE>
   <IEA>
   </IEA>
</ACTIS>
desadv_x12_856_4010.desadv_x12_856_4.xsl
Edit2.xml