squash with 'Trim: Minimum replicas includes good and stale'

docs/system_overview/data_objects.md

@@ -264,10 +264,11 @@ Trim refers to unlinking one or more replicas mapped to an existing data object.
 
 ![Trim](../images/trim_01.drawio.png)
 
-Trim requires 2 inputs:
+Trim requires 1 input:
 
 1. An existing data object with at least two replicas which are at rest and can be unlinked.
-2. A minimum number of replicas to retain.
+
+Trim requires a minimum number of replicas to remain at completion. The default minimum number of replicas to retain is 2.
 
 Trim selects stale replicas first - trimming from oldest to youngest - until the specified minimum number of replicas is reached. If more replicas can be trimmed, then the good replicas are trimmed from oldest to youngest, down to the specified minimum number of replicas. The specified number of replicas cannot be less than 1. In other words, trim cannot completely remove a data object.