diff --git a/pd-control.md b/pd-control.md
index 708461aab0c61..e4d91c64305ae 100644
--- a/pd-control.md
+++ b/pd-control.md
@@ -601,7 +601,9 @@ Usage:
 
 ### `region keys [--format=raw|encode|hex] <start_key> <end_key> <limit>`
 
-Use this command to query all Regions in a given range `[startkey, endkey)`. Ranges without `endKey`s are supported. The default value of `limit` is `16`, set to `-1` for unlimited. 
+Use this command to query all Regions in a given range `[startkey, endkey)`. Ranges without `endKey`s are supported.
+
+The `limit` parameter limits the number of keys. The default value of `limit` is `16`, and the value of `-1` means unlimited keys. 
 
 Usage: