diff --git a/config/example-extras.cfg b/config/example-extras.cfg
index 9eed2993..8b1cad33 100644
--- a/config/example-extras.cfg
+++ b/config/example-extras.cfg
@@ -970,8 +970,12 @@
 #[gcode_macro my_cmd]
 #gcode:
 #   A list of G-Code commands (one per line; subsequent lines
-#   indented) to execute in place of "my_cmd". This parameter must be
-#   provided.
+#   indented) to execute in place of "my_cmd". This parameter is
+#   evaluated using Python "string format syntax" with the command
+#   parameters as named arguments. For example, if one were to define
+#   a macro MY_DELAY with gcode "G4 P{DELAY}" then the command
+#   "MY_DELAY DELAY=100" would evaluate to "G4 P100". This parameter
+#   must be provided.
 
 
 # Replicape support - see the generic-replicape.cfg file for further