data: clarify FreshnessPeriod=0 semantics

refs #5268

Change-Id: I58ae182637a5377f3e54db69119a94a9620db51d
diff --git a/changelog.rst b/changelog.rst
index 7c8f197..be79186 100644
--- a/changelog.rst
+++ b/changelog.rst
@@ -38,7 +38,7 @@
 - **Data**
 
   + Make ``MetaInfo`` and ``Content`` elements optional
-  + Change semantics of omitted (or set to zero) ``FreshnessPeriod`` element: it cannot be used to satisfy Interests with ``MustBeFresh``
+  + Change semantics of omitted (or set to zero) ``FreshnessPeriod`` element: it cannot be used to satisfy Interests with ``MustBeFresh`` during content store lookup
 
 - **Signature**