All of the parts are separated into pieces to make 3d printing easier.
26+ Wall Line Count 3D Printing Images. Having a shell thickness of 0.8mm means a wall. This improves it some, but i suspect just by making it a little more difficult to see.
Ultimate Beginner's Guide to 3D Printing from static.makeuseof.com
Overall the print looks okay. Some of the parts, like the arms or the knobs, might have to be printed more than once. Thin features are impossible to 3d print unless they are larger than the minimum printable feature size for each technology.
To adjust overall shell thickness, you'll have to change the wall line count setting.
While there are no rules to setting a wall thickness as long as you wall thickness (also sometimes referred to as shell thickness) is simply the distance between one surface in your print and the opposite surface. There's a limit to how thin a part feature can be designed for 3d printing. I discovered to enable random start points for all. Wall line count (3 instead of 2):
