I noticed that too when I was checking my supercharger. A felt tip pen mark.
Balancing mark ,
With the superchargers that we have fitted bigger compressor wheels to , we found some would loosen the bearing section in use afterwards
the original assembly bolts were the problem and now we upgrade the bolts
The loose bearing section would make a lot of vibration and noise , quite obvious and easily addressed if not ignored
i havent tried it yet but think i could source replacement ceramic bearings and rebuild these if ever needed