There is a many-to-one relationship between the FactOrderDetails to DimCustomer tables.
Bi-directional relationship guidance
A bi-directional relationship is one that filters in both directions.
Generally, we recommend that you minimize the use of bi-directional relationships. That's because they can negatively impact on model query performance, and possibly deliver confusing experiences for your report users. [Not D] Note:
There are three scenarios when bi-directional filtering can solve specific requirements:
Special model relationships
Slicer options "with data"
Dimension-to-dimension analysis
Reference:
https://learn.microsoft.com/en-us/power-bi/guidance/relationships-bidirectional-filtering