diff --git a/Filer-Benchmark.md b/Filer-Benchmark.md
index 6ce75f2..e69eb85 100644
--- a/Filer-Benchmark.md
+++ b/Filer-Benchmark.md
@@ -3,11 +3,11 @@
 [Yahoo! Cloud Serving Benchmark(YCSB)](https://github.com/brianfrankcooper/YCSB) is a framework for evaluating the performance of different “key-value” and “cloud” serving stores.
 
 ## S3 is a poor key-value store
-It is a bit strange to evaluate a file system as a key-value store. However, I found AWS S3 is one of the stores supported. So I decided to try it out.
+It is a bit strange to evaluate a file system as a key-value store. However, I noticed AWS S3 is one of the stores supported. So I decided to try it out.
 
-But after dig deeper into it, I found the S3 is poorly implemented and not maintained. It is only a single threaded, the serialization/deserialization seems wrong, and the library is about 5 years old.
+But after digging deeper into it, I found the S3 is poorly implemented and not maintained. It is only single threaded, the serialization/deserialization seems wrong, and the library is about 5 years old.
 
-What is more, the API cost is a big concern. S3 seems cheap for storage, but for small objects which requires frequent access, the API can quickly add up.
+What is more, the API cost is a big concern. S3 seems cheap for storage, but for small objects which requires frequent access, the API cost can quickly add up at $0.005 for 1 thousand PUT/DELETE requests.
 
 If we need to test with 1 million objects:
   * 1 million write operations cost $5, or $150/month for 12 operations/second.