SRM method /SAPSRM/IF_PDO_DO_CHANGE_DOC~GET_CHANGE_DOCUMENTS subtracts 1 from version numbers of change documents

Hello Experts,

I'm using the method below to retrieve change documents of a PO, but it is subtracting 1 from the version change documents. Why is this?

Class: /SAPSRM/CL_PDO_BO_PO_ADV

Method: /SAPSRM/IF_PDO_DO_CHANGE_DOC~GET_CHANGE_DOCUMENTS

I was debugging the method and its subtracting 1 from the version number. For example if the PO is at version 3, its changed documents should be at version 3. This is the case within the method when it calls BBP_CHANGE_DOC_GET_NEW (Change document versions are at 3), but later in the method it subtracts 1 from all the versions not having "C". The change document versions will now be at 2 because of this. I would like to know why.

Thanks in advanced,

Jack