diff --git a/misc/OpenPGPMessageFormat.md b/misc/OpenPGPMessageFormat.md
index daaa715e..524798df 100644
--- a/misc/OpenPGPMessageFormat.md
+++ b/misc/OpenPGPMessageFormat.md
@@ -27,4 +27,8 @@ graph LR
     esks -- "SKESK|PKESK,k/k" --> esks
     esks -- "Sym. Enc. (Int. Prot.) Data,k/e" --> enc((Encrypted Data))
     enc -. "ε,e/m" .-> pgpmsg
-```
\ No newline at end of file
+```
+
+The dotted line indicates a nested transition.
+For example the arrow `Compressed Data,m/m` indicates, that the content of the Compressed Data packet itself
+is an OpenPGP Message.
\ No newline at end of file