diff --git a/alert-rules.md b/alert-rules.md
index d3b7eef544875..61fba8e2b4b31 100644
--- a/alert-rules.md
+++ b/alert-rules.md
@@ -121,7 +121,7 @@ This section gives the alert rules for the TiDB component.
 
 * Description:
 
-    The latency of handling a request in TiDB. If the ninety-ninth percentile latency exceeds 1 second, an alert is triggered.
+    The latency of handling a request in TiDB. The response time for 99% of requests should be within 1 second; otherwise, an alert is triggered.
 
 * Solution: