diff --git a/resources/templates/provision/grandstream/ht818/{$mac}.xml b/resources/templates/provision/grandstream/ht818/{$mac}.xml
index 408c539fd5..2d602692c8 100644
--- a/resources/templates/provision/grandstream/ht818/{$mac}.xml
+++ b/resources/templates/provision/grandstream/ht818/{$mac}.xml
@@ -597,7 +597,7 @@
     <!-- # Register Expiration (in minutes. default 1 hour, max 45 days) -->
     <!-- # Number: 1 to 64800 -->
     <!-- # Mandatory -->
-    <P32>{$account.1.register_expires}</P32>
+    <P32>{math equation="x / y" x=$account.1.register_expires y=40}</P32>
 
 
     <!-- # Reregister before Expiration (in seconds. Default 0 second) -->