Answer:
I think it changed from 36x to 48x
Depending on how you look at it, it could have changed from 3x to 4x or 36x to 48x.
If they said it was 18 feet instead of 18 inches, it would be 3x or 4x, but they had it as inches.
18 inches = 1.5 feet
72/1.5 = 48
54/1.5 = 36
So originally, it would have been a scale of 1 in : 36in , but it changed to 1 in : 48 in
Sorry if this was confusing.