replicas_per_primary and replicas_per_master

What is the difference between the replicas_per_master and replicas_per_primary given in this documentation, https://registry.terraform.io/providers/hashicorp/azurerm/latest/docs/resources/redis_cache#replicas_per_master

I am trying to identify what is the difference in the above two values and how they impact Redis configuration, any inputs would be very helpful