Clarify purpose of Sequence ID

dspace-api/src/main/java/org/dspace/content/ItemServiceImpl.java

@@ -496,7 +496,8 @@ public class ItemServiceImpl extends DSpaceObjectServiceImpl<Item> implements It
 
         super.update(context, item);
 
-        // Set sequence IDs for bitstreams in item
+        // Set sequence IDs for bitstreams in Item. To guarantee uniqueness,
+        // sequence IDs are assigned in sequential order (starting with 1)
         int sequence = 0;
         List<Bundle> bunds = item.getBundles();
 
@@ -513,8 +514,6 @@ public class ItemServiceImpl extends DSpaceObjectServiceImpl<Item> implements It
 
         // start sequencing bitstreams without sequence IDs
         sequence++;
-
-
         for (Bundle bund : bunds) {
             List<Bitstream> streams = bund.getBitstreams();
 
@@ -1561,4 +1560,4 @@ prevent the generation of resource policy entry values with null dspace_object a
         metadataValue.setLanguage(Item.ANY);
         return metadataValue;
     }
-}
+}