Why is the image size in the Media Library different than the image size returned by the API?

When checking the image's file size on a local machine (e.g. with Mac finder), or when using the Admin API:

cloudinary.v2.api.resource("public_id", function(res,err) {console.log(res,err)});

The size of the image is in Bytes. However when viewing the file size in the Media Library:

The size of the image is in Kibibytes.

You can convert between sizes using Google here:

https://www.google.com/search?q=1+kb+in+kib