Mac OS publishes size in powers of 10. Other operating systems like Windows, Linux publish sizes in powers of 2. Zoom also follows the norm of publishing size in terms of powers of 2.
[Mac] 1 KB = 1000 bytes
[Others] 1 KB = 1024 bytes.
To get the sizes in bytes rather than in more readable KB / MB / GB format, please use the “zm getmetadata” command-line client, and look for “ZPIG_Native File Size” property.