How does supply planning work with ranking sourcing rules for make at option?

Summary: How does supply planning work with ranking sourcing rules for make at option?

Content (required): we have the scenario likes this: for example there are 3 finished products can be produced by 3 factories. We set sourcing rules with ranking option. For example, rank 1 for factor1, rank 2 for factor 2, rank 3 for factor 3. Currently we are unable to understand the mechanism of system when derive production plan (MPS) for each factory. We don't know which criteria/rationale are used to arrange those items for each factory such as manufacturing cost, ...etc.

Version (include the version you are using, if applicable): 21C

Code Snippet (add any code snippets that support your topic, if applicable):