When testing the receive engine and when the serial number is to be removed, you need to change the action code attribute to actionCode="Delete". Note that while this removes the serial number from a tag, it does not delete the actual serial number.

<SyncAssets releaseID="1.2.1" versionID="4.0.0" languageCode="EN" xmlns="http://www.mimosa.org/ccom4" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:oa="http://www.openapplications.org/oagis/9">
  <oa:ApplicationArea>
    <oa:Sender>
      <oa:LogicalID>57ed9c9b-daf3-4424-b18a-a064e69fcda5</oa:LogicalID>
    </oa:Sender>
    <oa:CreationDateTime>2016-07-26T06:54:49Z</oa:CreationDateTime>
    <oa:BODID>b1c8a52f-bb26-4410-9254-30cad85450fb</oa:BODID>
  </oa:ApplicationArea>
  <DataArea>
    <oa:Sync>
      <oa:ActionCriteria>
        <oa:ActionExpression expressionLanguage="XPath" actionCode="Add">
          /SyncAssets/DataArea/Assets
        </oa:ActionExpression>
      </oa:ActionCriteria>
    </oa:Sync>
    <Assets>
      <Asset>
        <UUID>29a607c4-90f6-48fe-8fc6-4675478aa9b7</UUID>
        <Attribute>
          <UUID>ccc98f25-2ea1-4876-9870-f1365f78ec4f</UUID>
          <Type>
            <UUID>f36bcdef-ed93-aff3-ab34-36f8f06ba927</UUID>
            <ShortName>System</ShortName>
          </Type>
          <ValueContent>
            <Text>CTDB1</Text>
          </ValueContent>
        </Attribute>
        <ShortName>ABX-00000598</ShortName>
        <RegistrationSite>
          <UUID>30e16c3e-144c-48ca-b442-583e93af7b2d</UUID>
          <ShortName>001</ShortName>
          <FullName>Primary Plant</FullName>
        </RegistrationSite>
        <Manufacturer>
          <UUID>b2d2da52-cde4-4ce5-aef6-df172e45ae20</UUID>
          <ShortName>MANF-00033</ShortName>
          <FullName>Manufacturer A</FullName>
          <Type>
            <UUID>6ef5f3a7-5653-4a45-9591-beec23588b14</UUID>
            <ShortName>Manufacturer</ShortName>
          </Type>
        </Manufacturer>
        <Model>
          <UUID>1f7ecae8-0560-474a-bb6d-43721c7c7f3a</UUID>
          <ShortName>282815-2</ShortName>
          <FullName>282815-2</FullName>
          <Type>
            <UUID>1a6785ea-9036-48b5-8d9f-7b72db4d70af</UUID>
            <ShortName>JUNCTION BOX - INSTRUMENTATION</ShortName>
          </Type>
        </Model>
        <SerialNumber>TEX 801-2.12</SerialNumber>
        <AssetSegmentEvent>
          <UUID>b4c113df-9ba6-7334-e9f9-312602629a3c</UUID>
          <Type>
            <UUID>b4c113df-9ba6-7334-e9f9-312602629a3c</UUID>
            <ShortName>Serial Number Installation</ShortName>
          </Type>
          <Asset>
            <UUID>c6e52651-454a-4150-8378-ea605a787c04</UUID>
            <ShortName>00000598</ShortName>
          </Asset>
          <Segment>
            <UUID>ec2fa43e-75d7-4e96-a545-8f5bc09a8f11</UUID>
            <ShortName>ALER-1500401</ShortName>
          </Segment>
        </AssetSegmentEvent>
      </Asset>
    </Assets>
  </DataArea>
</SyncAssets>