add javadoc

iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/common/MPPQueryContext.java

diff --git a/iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/common/MPPQueryContext.java b/iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/common/MPPQueryContext.java
index 13773c1..cc9ad82 100644
--- a/iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/common/MPPQueryContext.java
+++ b/iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/common/MPPQueryContext.java
@@ -189,7 +189,10 @@
     return queryType;
   }
 
-  /** the max executing time of query in ms. Unit: millisecond */
+  /**
+   * Returns the total query timeout in milliseconds, measured from {@link #getStartTime()}. This
+   * value never represents the remaining timeout.
+   */
   public long getTimeOut() {
     return timeOut;
   }