Remove Duplicates

Hi,

I have a problem using the Remove Duplicates Operator. Here is my workflow:

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<process version="5.0">
  <context>
    <input/>
    <output/>
    <macros/>
  </context>
  <operator activated="true" class="process" expanded="true" name="Process">
    <process expanded="true" height="646" width="1095">
      <operator activated="true" class="read_excel" expanded="true" height="60" name="Read Excel" width="90" x="45" y="30">
        <parameter key="excel_file" value="E:\RM\Test_Duplicates.xls"/>
        <list key="annotations"/>
      </operator>
      <operator activated="true" class="set_role" expanded="true" height="76" name="Set Role" width="90" x="179" y="30">
        <parameter key="name" value="CID"/>
        <parameter key="target_role" value="id"/>
      </operator>
      <operator activated="true" class="remove_duplicates" expanded="true" height="76" name="Remove Duplicates" width="90" x="313" y="30">
        <parameter key="attribute_filter_type" value="single"/>
        <parameter key="attribute" value="CID"/>
        <parameter key="include_special_attributes" value="true"/>
      </operator>
      <connect from_op="Read Excel" from_port="output" to_op="Set Role" to_port="example set input"/>
      <connect from_op="Set Role" from_port="example set output" to_op="Remove Duplicates" to_port="example set input"/>
      <portSpacing port="source_input 1" spacing="0"/>
      <portSpacing port="sink_result 1" spacing="0"/>
    </process>
  </operator>
</process>

And here is the table I am using to test it.

CID Value
3596 X
4054 X
4054 X
3000 S
32135 S

When I use it with invert selction to get the duplicates only it gives me 2 examples which are not duplicate. Could someone tell me where I go wrong?

Cheers,
Markus