

There’s a response from someone at Apple Community support that explains what might be happening.
FWIW, “System Data” is not just space used with macOS system applications but it is also contains user data that does not neatly fit into one of the other categories. Often a lot of this but not all can be found in the hidden user’s Library folder (accessed by holding down the Option key and selecting the “Go” menu in Finder.
If you open this folder look at the size of the “Application Support” folder. Depending on your apps, they could be storing a lot of data in these folders. Before messing with anything in these folders, you need to go to the application developer site and see what can be done with them. Some apps can allow certain portions of that data to be located on an external drive.
As for the amount you are seeing, 50-60 GB is not unusual for “System Data”.
Here’s the link. There’s not much more there but I like to share where I got the quote from.
Good luck!








Not Trek related but this reminded me of an old gem from Adult Swim.
Senior Mutant Ninja Turtles
https://youtu.be/BdBPpg0DdrI
I swear it was originally called Geriatric Ninja Turtles but I might be mixing this up with something else.