What does it mean that xxx Mb is purgeable?

What is 'Other' and 'Purgeable' in About This Mac? - Apple Support

In macOS Sierra, “Purgeable” content appears when you've turned on Optimize Mac Storage. It's storage space that your Mac can automatically make available when storage space is needed. Files marked as purgeable can always be downloaded again on demand.

You shouldn't use CleanMyMac, it's garbage that can do you no good and a lot of harm.

How to free up storage space on your Mac - Apple Support

If you're low enough on free space reading purgeable or not you're way to low. I don't know SpaceGremlin but I find the free Omni DIskSweeper very reliable and easy to use. https://www.omnigroup.com/more

Thank you for the response, Barney. Nevertheless, is there a way to get rid of data that the Sierra considers "purgeable"? For some reason, as I delete data Sierra adds that to the purgeable portion of the "available" space instead of counting that space as truly "free". Some applications do not consider purgeable data as true free space and will not run if the true free space is less than their requirements. Utilities such as SpaceGremlin Pro and CleanMyMac3 do not recognize it either. I have also used Terminal to determine that this is not a time machine snapshot problem for me. Any suggestions?

Rick, how can I delete data that is considered "purgeable" to create "true" free space? I have applications that will not regard purgeable data as "free" and will not run. Thanks!

You don't, unless you think that file, or picture, or whatever is garbage and you no longer want it.

Purgeable does not equate to unwanted.

Putgeable space is not free space.

Nothing that is purgeable is actually free of data.