When I model something in blender to be 3d-printed, I always get wrong dimensions in stl file, even though I've set scene units to metric, scale to 1 and in blender viewport, it shows the correct dimmensions.

But when I convert and export the model to an stl file, dimensions get converted to millimeters, no matter the settings or model dimensions in blender.

For exporting blender model to stl files, I am using a blender addon named '3D Print Toolbox'. At first, i thought I need to change some setting in the addon, but couldn't find anything to play around with.

My real problem/question is - Is there something that I am missing or doing wrong?
Perhaps some setting or step that I am overlooking before exporting.
PS: As a workaround, each time, I have to scale up the exported stl file model.