free space differ in info and "about this mac"

[guido.coza]

I SADLY recently updated from Mavericks to sierra and had to downgrade to Yosemite. What a mess!!
I feel like an Wicrosoft user all over again, but that is not the point!
There is a new feature in yosemite that lets you check "storage" in About my mac. There it states that I have 15GB of 121GB free space available.
The HD/SSD icon and "info" however gives me 36GB free space!??
why the difference and can I somewhere see the "purgeable" space one can check in Sierra ??

 

[jav6454]

There are two ways to calculate storage space, one is to count via Gigabytes (1 byte = 8 bits and 1 Gigabyte is 1024 MegaBytes, recall that 1 Megabyte is 1024 Kilobytes and that 1 KiloByte is 1024 Bytes), basically power of 2.

The other method is to just go straight into the Giga- Mega- Kilo- prefixes and calculate space not in power of 2 but in power of 10.

Both are correct in either case, you just need to understand which one you are reading.

[...]

Also wrong forum, this is iOS, not Mac OS X forum.

 

[guido.coza]

Yxs Jav and sorry for forum mixup