diff --git a/Filer-Redis-Setup.md b/Filer-Redis-Setup.md
index dc50775..3d30bd9 100644
--- a/Filer-Redis-Setup.md
+++ b/Filer-Redis-Setup.md
@@ -23,7 +23,11 @@ This is where `redis3` can help. The internal data structure is:
 ```
 The directory list is stored as a skip list, and the child names are spread into the list items. This prevents each directory entry from being too large and slower to access. Skip list has `O(log(N))` access time. With each sorted set storing 1 million names, it should scale very well to billions of files in one directory.
 
-Compared to `redis2`, there are extra cost to maintain this list:
+Compared to `redis2`, there are extra Redis operations to maintain this list:
 * Adding or deleting needs one additional lock operation.
 * Updating an entry needs to takes `O(log(N))` times to access the skip list item first.
-So no need to jump to `redis3` in a hurry unless you have to.
+
+One Redis operation cost 25 microseconds. The extra Redis operations cost about 100 microseconds when run with 1 million items. It is relatively a tiny cost to pay compared to the whole file creation/update/deletion process. 
+
+# Note
+The file read operation is still just one Redis operation, since it does not need to read the list of other directory items.
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