Update README.md

Describing the change more accurately.

definitions/region/README.md

@@ -143,17 +143,21 @@ Example:
 > Norway>Germany
 
 To represent data that refers to a flow or cost contribution of a region
-to a connection between two regions, the third contributing region name 
+to a connection between two regions, the contributing region name 
 can be combined with the bi-directional data using a `:` character before
 the bi-directional data (without spaces before/after that character).
 
-The third contributing region can be of **a different level of spatial detail**
-from the bi-directional data.
-
 Example:
 
 > Germany:France>Spain
 
+The contributing region can be of **a different level of spatial detail**
+from the two regions specified in the bi-directional data.
+
+Example:
+
+> Berlin:France>Spain
+
 ## Parallel connections of directional data
 
 When timeseries data represents flows or capacity on one of several parallel