Hello, macOS shows the wrong free space for many reasons, like the local snapshot of Time Machine, the purgeable space on Mac, system glitches, disk errors, and so on. So let's fix this problem:
(1)Empty the Trash.
(2)Restart your Mac.
(3)Remove purgeable space. You are suggested to utilize iBoysoft DiskGeeker, which can help you remove purgeable space cleanly and completely.
- Download and install it.
- Select the target drive from the startup disk.
- Choose Clean Junk from the right toolbar then select purgeable files and click Clean > OK.
(4)Try Safe Mode.
(5)Reindex Spotlight.
(6)Repair the drive with First Aid.
Hope you can fix your problem in the end.
Also read: macOS Shows Wrong Free Space in Disk Utility