As detailed in https://www.omg.org/spec/UML/2.2/Superstructure/PDF/ e. g. Figure 7.51 - Other power type examples, this may be used to symbolize disjoint partitioning.
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Hello R.,I don't know if that answers, but you can see similar example here, but for all arrow (or depending of a threshold)...
If that can help,Regards,Th.