Improved some comments.

Author: SteveIves

CodeGenEngine/RepositoryTools.dbl

@@ -424,11 +424,12 @@ namespace CodeGen.Engine
                                 end
                             end
 
-                            ;; Finally remove the group field from the structure
+                            ;; Remove the array field from the structure
                             Struct.Fields.RemoveAt(ix)
 
-                            ;; And process this index again (it's now the first field from the array)
+                            ;; And process the same index again, it's now the first field from the array
                             ix-=1
+
                             nextloop
                         end
                     end
@@ -441,6 +442,18 @@ namespace CodeGen.Engine
                     if (Field.GroupType==RpsFieldGroup.No)
                         nextloop
 
+
+                    ;; ----------------------------------------------------------------------------------
+                    ;; If we get here then we have one of four types of GROUP field:
+                    ;;
+                    ;; 1. Explicit GROUP (fields defined locally)
+                    ;; 2. Implicit GROUP (fields defined by another structure)
+                    ;;
+                    ;; And if the "include overlays" command line option (-f o) was used:
+                    ;; 
+                    ;; 3. Explicit GROUP OVERLAY
+                    ;; 4. Implicit GROUP OVERLAY
+
                     ;; Is it an explicit group and we've been told not to expand them?
 
                     if (Field.GroupType==RpsFieldGroup.Yes && String.IsNullOrWhiteSpace(Field.GroupStructure) && context.CurrentTask.ExplicitGroupNoExpand)