Hmm ok, I will log a bug against this and have the team check it out. Is it just mis-leading or is it blocking any functionality for you?
Found another cosmetic bug:
Go to Admin > Create Group, give it a name, Show Only Nodes / Group by Building. If you have two building custom properties, but one is upper-case and one is lower-case (e.g. "Plt11" and "PLT11", no quotes), it lists them as two different entries with a differen number beside them, but when you expand them they have the same members. These should be merged (as they are elsewhere in NPM) and be case-insensitive.