docs: Documentation update

Change-Id: I6f916eb822a59e980e8fb1134886c3431755119c
diff --git a/model/cs/content-store-with-probability.hpp b/model/cs/content-store-with-probability.hpp
index eabe12d..5ba9b58 100644
--- a/model/cs/content-store-with-probability.hpp
+++ b/model/cs/content-store-with-probability.hpp
@@ -35,7 +35,8 @@
 
 /**
  * @ingroup ndn-cs
- * @brief Special content store realization that honors Freshness parameter in Data packets
+ * @brief Special content store realization that probabilistically accepts data packet
+ *        into CS (placement policy)
  */
 template<class Policy>
 class ContentStoreWithProbability