Clarify IPv4 and IPv6 configuration

CONFIGURATION.md

@@ -10,18 +10,18 @@ via the `--config` argument.
 
 Address to listen for connections on in the format of `interface:port`.
 
-### Listen on localhost
+### Listen on all addresses (IPv4 and IPv6)
 
-`localhost:1965`
+`:1965`
 
-### Listen on an IPv4 or IPv6 address
+### Listen on a specific address (IPv4 or IPv6)
 
 `192.0.2.1:1965` or `"[2001:db8::1]:1965"` (please note the quotes and brackets
 for IPv6 addresses).
 
-### Listen on all interfaces
+### Listen on localhost (IPv4 only)
 
-`:1965`
+`localhost:1965`
 
 ## Types