Availability not match with actual used in Extreme SSD

Portable SSD Portable | Extreme | Extreme Pro SSD
1

I am using the SanDisk Extreme Portable SSD 1TB, it shows my available storage is 52GB.

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image494×506 42 KB

However, I only used 246 GB, here is the breakdown
246.1 GiB [##################] /Extreme SSD

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image1218×418 82.7 KB

Where is the rest storage gone? It is an 1TB hard disk but I only used 246 GB and 52GB left, may I ask why?

2

Several reasons can cause macOS to display incorrect free space, including local snapshots of Time Machine, purgeable space on the Mac, disk errors, and others. Try the following steps to fix this problem:

  1. Empty the Trash. If your Mac shows less space on the SanDisk Extreme Portable SSD after deleting files, the deleted items are likely still in that drive’s specific Trash folder, holding space until you empty it. Empty the Trash, then restart your Mac and see if the external SSD shows correct free space.
  2. Remove purgeable space. You are suggested to use a disk utility app to remove purgeable space cleanly and completely.
  3. Repair the external SSD. You can try Disk Utility’s First Aid to check and repair disk errors, and re-check the free space.

Also read: macOS Shows Wrong Free Space in Disk Utility