Image resolutions

I am a new user of LibRaw and I like very much what I see here so far, so thanks for the great work :)
Currently, I work with Canon cameras and the Canon SDK. When downloading and developing an image from eg a Canon 550D, its SDK will tell me that the image resolution for a still image is 5184 x 3456, which is also confirmed here:
However, when I use the newly integrated LibRaw 0.10-Beta2:

EdsStreamRef downloadStream;
EdsCreateMemoryStream( 0, &downloadStream );
EdsDownload( _directoryItem, dirItemInfo.size, downloadStream );
EdsDownloadComplete( _directoryItem );

void* pBuffer = NULL;
EdsGetPointer( downloadStream, &pBuffer );
EdsUInt32 bufferSize = 0;
EdsGetLength( downloadStream, &BufferSize );

LibRaw libRaw;
libRaw.open_buffer( pBuffer, BufferSize );
libRaw.imgdata.params.output_tiff = 1;
libRaw.dcraw_ppm_tiff_writer( "C:\\test.tiff" );

The image resolution returned increases to 5202 x 3465. Can someone please explain to me why there are more pixels using LibRaw than there are from the Canon SDK? Also, is there a way to alter LibRaw so that I can get the same resolution image that I would have expected?
Once I get up to speed with how your software works I would like to contribute as well, if that is possible.