update docs after FasterXML/jackson-databind@5087367a0
diff --git a/src/main/java/com/fasterxml/jackson/annotation/JsonFormat.java b/src/main/java/com/fasterxml/jackson/annotation/JsonFormat.java
index 99e5b6f..c4868b7 100644
--- a/src/main/java/com/fasterxml/jackson/annotation/JsonFormat.java
+++ b/src/main/java/com/fasterxml/jackson/annotation/JsonFormat.java
@@ -43,7 +43,15 @@
* will not work as per-property annotation.
* </li>
*</ul>
- *
+ * In Jackson 2.4:
+ * <ul>
+ * <li>{@link java.lang.Number} subclasses can be serialized as full objects if
+ * {@link Shape#OBJECT} is used. Otherwise the default behavior of serializing to a
+ * scalar number value will be preferred. NOTE: can ONLY be used as class annotation;
+ * will not work as per-property annotation.
+ * </li>
+ *</ul>
+ *
* @since 2.0
*/
@Target({ElementType.ANNOTATION_TYPE, ElementType.FIELD, ElementType.METHOD, ElementType.PARAMETER,