diff --git a/x11.md b/x11.md
index 537fae7..b5aaeeb 100644
--- a/x11.md
+++ b/x11.md
@@ -6,7 +6,7 @@ Build:
 
     ./run -x
 
-We don't build X11 by default because it takes a considerable amount of time, and is not expected to be used by most users.
+We don't build X11 by default because it takes a considerable amount of time (~20%), and is not expected to be used by most users.
 
 Inside QEMU: