diff --git a/private/compat/31.0/31.0.cil b/private/compat/31.0/31.0.cil
index 0e90912..b0df314 100644
--- a/private/compat/31.0/31.0.cil
+++ b/private/compat/31.0/31.0.cil
@@ -9,6 +9,7 @@
 (type vr_hwc)
 (type vr_hwc_exec)
 
+;; mapping information from ToT policy's types to 31.0 policy's types.
 (expandtypeattribute (DockObserver_service_31_0) true)
 (expandtypeattribute (IProxyService_service_31_0) true)
 (expandtypeattribute (aac_drc_prop_31_0) true)