If the Space Modules lets you have duplicate numbers then the Space Type's naming has not been set to unique.

Complete the following:

1. Navigate to Admin > Space Hierarchy.
2. Navigate to the space type.
3. Click the space type. The Edit Space Type form displays.
4. Check the Name must be unique check box.

5. Click the Update Space Type button.

For more details, see Add, Edit, or Delete the Space Types.