Document the reduced retry interval

source/includes/webhooks.md

@@ -136,7 +136,8 @@ receive an HTTP 200 response within 30 seconds.
 The system retries at exponentially-increasing intervals equal to
 (failure_count^4 + 3) seconds. This means that delivery will be retried 4
 seconds after the first failure, 19 seconds after the second, 84 seconds after
-the third, 259 seconds after the fourth, and so on until it succeeds.
+the third, 259 seconds after the fourth, and so on. When the retry interval hits
+one day the system will attempt sending once daily until it succeeds.
 
 ## Responding to a webhook request