Thank you for your further explanation. A system process is basically result of an LCA calcualation, and summarises all inputs and outputs of a life cycle; not the impacts, but the flows, i.e. the resources and emissions. When you have calculated a product system, you can save the results as a system process. You can try that and you will see the differences, a system process typically has many more inputs and outputs than a unit process.
For the process contribution in the project report, you will only see those processes that are part of your product system. If you have system processes in your product system, you will see those, if not, not.
I hope this helps a bit?