Yes, this is a limitation that was set in Archicad, you can not have scales smaller than 1:30 000, and scales larger than 1:1 (for example, 2:1, which would require entering 0.5 in the field in the Scale Dialog).
I am not sure, but this may have to do with the internal accuracy of the program, so with scale out of this range, Archicad would start having accuracy issues? But as I said, I am not sure about this.
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