You got it - when I looked at your file it implied the object had those dimensions. Not really sure about the 85mm and 25mm and how that relates.
I can't really help with Autocad, but in general there are several options:
1. Change your settings in Autocad so that the stl export matches the internal dimensions (no idea...);
2. Just scale your model by 10 (or 8.5 or whatever factor you desire) and re-export;
3. Open the .stl file in Netfabb Basic (free!) and scale it in there. This package is very useful in 3d modelling and allows you to make all sorts of checks on your model.