update file name conventions

for book objects:
3 digits for less than 1000 files
4 digits for 1000 or more files

metadataguidelines.md

@@ -51,8 +51,11 @@ This document is intended as a guide to data entry and descriptive cataloging fo
   *  Enter the folder name that contains the media
   *  The folder name must be the same root as the file name
 
-      Folder name = Mss_Coll_190_001  (this is entered in the _file_ field only)  
-      Filenames within folder = Mss_Coll_190_001-001.tif, Mss_Coll_190_001-002.tif, etc.
+      Folder name = Mss_Coll_190_001 (this is entered in the _file_ field only)  
+      Filenames within folder in server/external drive = Mss_Coll_190_001-001.tif, Mss_Coll_190_001-002.tif, etc.
+
+   *  For all book objects that contain less than 1000 pages/files, use three digits after separator (-)
+   *  For all book objects that contain 1000 pages/files or more, use four digits after separator (-)   
 
 * If you are uploading multiple **Single Graphics, Audio, or Video objects**, the file column should be formatted:
   *  Enter the appropriate **directory path** and individual filename with file extension.