diff --git a/docs/manual.md b/docs/manual.md
index 50a436bb..e8f1b908 100644
--- a/docs/manual.md
+++ b/docs/manual.md
@@ -744,5 +744,6 @@ The protected procedure payload should be considered as analogous to function ar
 The limitation on the number of protection domains in the system is relatively arbitrary.
 Based on experience with the system and the types of systems being built it is possible for this to be increased in the future.
 
-The limitation on the number of channels for a protection domain is based on the size of the notification object in seL4.
-Changing this to be larger than 64 would most likely require changes to seL4.
+The limitation on the number of channels for a protection domain is based on the size of the notification word in seL4.
+Changing this to be larger than 64 would most likely require changes to seL4. The reason for why the limit is not a
+power of two is due to part of the notification word being for internal libmicrokit use.