As the tutorial started, I saw how odd 104 looked on the vault door... more like 1 04.
Then I had to close the app because of some distraction.
When I returned, the vault number was gone as I hadn't really started the vault because of the interrupted introduction.
So I opted for 904 then, which looks great, but doesn't fit the canon.
Well, now that I'm at more than 60 residents, I'll have to keep that number.