External SSD disk purgeable data

If the catalog folder is on that external volume, the most important file to look at for space saving is the one in the catalog folder with a filename that ends in: 

…Previews.lrdata

That is the Lightroom Classic previews cache, and it’s completely purgeable and expendable. If it is now much larger than any other file in the catalog folder, you can delete it to free up lots of space. Because it’s a cache, deleting it does not delete any critical data, and Lightroom Classic will start rebuilding it the next time you browse images.

I noticed that even though I deleted close o 2,500 RAW pics at 61 mpxl each I have not seen any reduction in space usage. Moreover the 'purgeable' GO keep increasing. I do not know whether I should delete the purgeable space or even how to.

By @Lise34734661z2ty

(You may know some of this already)

A file can be deleted from a Lightroom Classic catalog at two levels: 

It can be deleted from the catalog. 

It can be deleted from the catalog and the file system. 

If a file is only deleted from a catalog, the file may still exist in its folder in the file system so it still takes up space.

If a file is deleted from a catalog and the file system, then the file is moved to the macOS Trash, but it still takes up space until the Trash is emptied. 

On macOS, emptying the Trash may not free up as much space as expected if the volume is backed up using software that maintains local backup snapshot files (such as but not limited to Apple Time Machine). These are automatically created and purged by the backup software as needed. They are invisible in the Finder because (like most files called “purgeable”) we are not expected to manage them manually, they’re automatically purged periodically. However, it’s possible to delete local snapshots manually using Apple Disk Utility or the backup software. Similar to the Lightroom Classic previews file, after being deleted they will re-appear normally.