PI mapping for extrinsic Ariba fields

I have a scenario where I'm converting a cXML source file into iDOC target file. Mapping is as shown above.

Input cXML:

          <ShipNoticeItem>

                     <Extrinsic name="harmonisedSystemNumber">12345678</Extrinsic>

                     <Extrinsic name="miscAmt1">50</Extrinsic>

                     <Extrinsic name="pack">20</Extrinsic>

                     <Extrinsic name="miscCharge2">12X10X2</Extrinsic>

                     <Extrinsic name="Misc">KG</Extrinsic>

                  </ShipNoticeItem>

.......................................

                     <Extrinsic name="harmonisedSystemNumber">234567</Extrinsic>

                     <Extrinsic name="miscAmt1">40</Extrinsic>

                     <Extrinsic name="pack">30</Extrinsic>

                     <Extrinsic name="miscCharge2">25X5X50</Extrinsic>

                     <Extrinsic name="Misc">KG</Extrinsic>

         </ShipNoticeItem>

.....................................................

                     <Extrinsic name="harmonisedSystemNumber">456789</Extrinsic>

                     <Extrinsic name="miscAmt1">60</Extrinsic>

                     <Extrinsic name="pack">80</Extrinsic>

                     <Extrinsic name="miscCharge2">50X20X10</Extrinsic>

                     <Extrinsic name="Misc">KG</Extrinsic>

                  </ShipNoticeItem>

.........................................................

Current output:

E1EDP09

     ZE1EDP09

          BRGEW=50

...........

E1EDP09

     ZE1EDP09

          BRGEW DOES NOT EXIST

..............

E1EDP09

     ZE1EDP09

          BRGEW DOES NOT EXIT

.............................................................................

Expected output:

E1EDP09

     ZE1EDP09

          BRGEW=50

........................

E1EDP09

     ZE1EDP09

          BRGEW=40

.............

E1EDP09

     ZE1EDP09

          BRGEW=30

Can anyone tell me what I'm doing wrong?

PS: This is the Ariba ASN interface. I'm using PI 7.1