Add correct lat/lon example; closes #471

Author: evanp

ERRATA.md

@@ -4,8 +4,20 @@ This document includes errata for the [Activity Streams](https://www.w3.org/TR/a
 
 ## Activity Streams
 
-- None yet reported.
+  - None yet reported.
 
 ## Activity Vocabulary
 
-- None yet reported.
+  - Example 150 has `latitude` and `longitude` properties with string values.
+    The range of these properties is `xsd:float`. A correct example would be:
+    
+    ```json
+    {
+      "@context": "https://www.w3.org/ns/activitystreams",
+      "type": "Place",
+      "name": "San Francisco, CA",
+      "longitude": 122.4167,
+      "latitude": 37.7833
+    }
+    ```
+