Clear up a couple things

docs/configuration.md

@@ -563,16 +563,16 @@ Apart from these, the following properties are also available, and may be useful
   <td><code>spark.default.parallelism</code></td>
   <td>
     For distributed shuffle operations like <code>reduceByKey</code> and <code>join</code>, the
-    largest number of partitions in parent RDD.  For operations like <code>parallelize</code> with
-    no parent RDDs, it depends on the cluster manager:
+    largest number of partitions in a parent RDD.  For operations like <code>parallelize</code>
+    with no parent RDDs, it depends on the cluster manager:
     <ul>
       <li>Local mode: number of cores on the local machine</li>
       <li>Mesos fine grained mode: 8</li>
       <li>Others: total number of cores on all executor nodes or 2, whichever is larger</li>
     </ul>
   </td>
   <td>
-    Default number of output partitions for operations like <code>join</code>,
+    Default number of partitions in RDDs returned by transformations like <code>join</code>,
     <code>reduceByKey</code>, and <code>parallelize</code> when not set by user.
   </td>
 </tr>