Hi,
STL does not contain unit information. That means if your workspace is set to inches, and you create a 1x1x1 inch cube, if you load it to your slicer, it will interpret it as a 1x1x1 mm cube. Because STL format is crap. Never meant to be an input format. Really sad that 3d printing does not have a decent mesh format. So the solution is to scale your model once you loaded it to the slicer. Or set the units to mm in Shapr.