STL does not contain any unit information. Only numbers. This means that if you export to STL, it does not matter what units you used. This is not specific to Shapr, this is how it works in every modeling tool. I suppose you are trying to import it to a slicer - you will have to scale the model properly. It is quite unfortunate that STL has become the standard for 3d printing and for other manufacturing tools, but this is how it works Hopefully someone will come up with a much better file format soon.