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Notes in FSM always refers to the second line of the long text of SAP ERP order. However, in this case, second line of the long text is also shown in subject above but will be truncated once it reaches the 512 byte limit.
Please also note that the idoc display (like tcode: WE05) will not show the entire length of the text as it's max segment length is 132, hence the need to use the output transformation tool to view the entries.