When you add a tag or comment to your scene, it is automatically assigned a unique ID. If, however, you are appending or merging multiple Autodesk Navisworks files together, then there is a possibility for the same ID to be used more than once. Consider the following example. Three users reviewed and added comments and markups to same model file, each saving their work as an NWF file. If you merge the resulting NWF files together, only one copy of the geometry would be loaded and any tag viewpoints of the same name would be suffixed with the NWF filename in brackets. All tag IDs, however, would be retained. In such cases, you can renumber all the IDs, making them unique to the scene once again.