diff --git a/offlineimap.conf b/offlineimap.conf
index 3ea9817..95611f0 100644
--- a/offlineimap.conf
+++ b/offlineimap.conf
@@ -1191,10 +1191,11 @@ remoteuser = username
 # This option stands in the [Repository RemoteExample] section.
 #
 # If offlineiamp is having troubles to download some UIDS, it's possible to get
-# them ignored in a list.
+# them ignored in a list. This only ignore the download.
 #
-# The function must return the list of UIDs to ignore, None otherwise. It is
-# passed the folder name.
+# The function must return the list of UIDs (integers), None otherwise. It is
+# passed the folder name (using the remote name with the remote separator,
+# likely '/').
 #
 #copy_ignore_eval = lambda foldername: {'INBOX': [2, 3, 4]}.get(foldername)