@siracusa Thanks for the tip!

I don't think System Settings is telling the full truth because according to Grand Perspective this one item (supposedly only 51GB) is as proportionally big as it is in the report.

One does not fill a 1TB drive with two dozen 51GB sections.

This seems to comply with the colored sections of the earlier readout which make total sense to me. Still no idea what the "System Data" usage is.

Also GP reports 100GB free while Finder says 11GB.

Will keep digging.

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