When exporting all materials from Revit into LightStanza, ceilings, walls, and floors have reflectance values of 80/50/20 by default. You can turn this feature off in LightStanza Account Settings by unselecting "Automatic Default Reflectance Values for Revit Models". This will allow for future imports to bring in reflectance values as determined in Revit.
TIMELINE
0:22 Export model from Revit
0:33 how to double check default reflectance values
0:52 changing default reflectance values
1:18 turning off default reflectance values from Revit