diff --git a/src/USER-ACKLAND/README b/src/USER-ACKLAND/README
index fedf5fbbb8..d44890ed3b 100644
--- a/src/USER-ACKLAND/README
+++ b/src/USER-ACKLAND/README
@@ -16,3 +16,11 @@ PRB(2006)73:054104.
 The output is a number with the following mapping:
 
 enum{UNKNOWN,BCC,FCC,HCP,ICO};
+
+or in other words:
+
+0 == UNKNOWN
+1 == BCC
+2 == FCC
+3 == HCP
+4 == ICO