Disk sizes reported wrongly?

I've begun to notice that ALL disks connected to my Mac are reported as having incorrect sizes. For example, the screenshot posted below is a 32GB SD card. It correctly states that the capacity is 31.9 GB. But it says that I have 35.66 GB of free space even though I already have 1.57GB of data on the card. WTF??? Is my Mac OS broken? Or is it just being dumb? I have tried to put 34-ish GB of data on the card to test but it won't let me, because the card is actually 31.9 GB and not like 37 or so as the macOS thinks. It does not seem to matter how the card itself is formatted (Fat32, exFAT, HFS+, etc etc).

That is wild! Does reformatting the SD card does not fix it? Could be a corrupted card. Is it only this one card or all SD cards, or just some SD cards? I mean, is it card specific or anything? That is so weird...

I've tried reformatting to several different formats and it always comes back like that. Even a brand new thumb drive (the one pictured in my original post) showed up like that. But it's for most (not all) every SD card and also my main drive. Here's some other pics:

wow... I'm stumped...

Hi.

Are the results the same if you try this on another machine?

Hi Joe
This is the way that the OS calculates file sizing now. If you subtract the "purgeable" from the available and then add to the used, it will be roughly equivalent. So the question is, "What does the "purgeable" data reflect.
Mostly, but not all is accounted as the file sizes for all the files with "Hard Links". If you have hard links, the purgeable size increases for each link to file by the file size it points to.
A much better and thorough explanation can be found here… eclecticlight.co/2019/02/09/finder-cant-...-hard-links-confuse/

Hope this Helps, Greg

Greg's comments are useful, but I don't think that is the answer to this issue. In no case should available space exceed the drive or disk capacity, so something else is going on. You might try resetting the system SMC as well as NVram/Pram. This can cause quirky problems from time to time.

support.apple.com/en-us/HT201295

Another test might be to create a new admin user and see if you get the same results.

I don't see that on any of our Macs. Yeah, that's not what VidGreg is referring to, different issue. I have heard of this issue once before, some time ago. Didn't pay it much mind, thought it was a once in a lifetime fluke.

DG, I should have been clearer, and I agree with you, it should always report actual capacity. I do think this is a bug but it is caused by how the OS is dealing (incorrectly) in reporting drive capacity by adding the purgeable size.
The article I linked to is titled "Finder can’t total file sizes correctly: how hard links confuse". And as I stated, a much better explanation.
This is a programming bug, IMHO
Haven't found solution, but I haven't had any negative issues. Maybe if your card/drive is very full, and you think you have more space??
I have also seen this like here on my SD card holding my Sound Libraries…



The Finder is reporting ~3.07GB over Capacity of the card. Same as the "purgeable".
So this is a current issue. but is appearing on multiple OSs. I'm on High Sierra, but my new SD card is a recent creation. Issue is on my old card too!

Hope this Helps, Greg