Field help (PSHCCE1) 

The analytical dimensions are initialized in compliance with the Default dimensions setup (PSD dimension code) linked to purchase requests. These dimension codes can be modified manually if authorized by the transaction.

When an analytical dimension type is used for the Project management tracking, then any modification of the project code made at header level will be redistributed to the lines; if the modification applies to a document line, then the dimension code of the dimension type will be reset. This reinitialization is compliant with the Default dimensions setup.