STL does not contain any unit information. Only numbers. This means that if you export your object to STL, it doesn't save the unit, just the numbers. This problem is not specific to Shapr3D, but rather a property of the file format.
The problem can occur in a slicer when the exported objects were created in an inch unit system, and the slicer's default units are centimeters. The quick fix for this problem, if you properly scale your object in the slicer or synchronize the unit system across your workflow.
When you are exporting an STL from the app, you will have the chance to set your units in the STL settings:
Set here the desired units, ideally the one your slicer has set as well.