To read the json.bz2 files you can use the following code in python:

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#!/usr/bin/env python

import json, bz2
from pymatgen.entries.computed_entries import ComputedStructureEntry

with bz2.open("2021.04.06_scan.json.bz2") as fh:
  data = json.loads(fh.read().decode('utf-8'))

entries = [ComputedStructureEntry.from_dict(i) for i in data["entries"]]

print("Found " + str(len(entries)) + " entries")
print("\nEntry:\n", entries[0])
print("\nStructure:\n", entries[0].structure)
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The meaning of the columns in ps_scan_summary.txt is

 1. chemical composition
 2. number of sites
 3. total energy per atom calculated in PBE functional at the PBE
    geometry (extracted from the primary dataset)
 4. the total energy per atom calculated with the PBEsol functional at
    the PBEsol geometry
 5. total energy per atom calculated with the SCAN functional at the
    PBEsol geometry
 6. volume of unit cell optimized with the PBE functional (extracted
    from the primary dataset)
 7. volume of unit cell optimized with the PBEsol functional
 8. band gap calculated with the PBEsol functional
 9. band gap calculated with the SCAN functional
10. total magnetic moment per atom calculated with the PBEsol functional
11. total magnetic moment per atom calculated with the SCAN functional
12. (3 values) diagonal of the stress tensor calculated with the SCAN functional