Two small notes:
1) If total size of maps in XX Gb it is means in bytes - XX*1024*1024, if size in XX Mb - XX*1024 for bytes.
2) For most NT maps the realy size of loaded maps is some more cos Mapsource do not take to attention generated MD2 and TRF section. For example, it is aproximately 50 of added Mb for all Europe.