As you can see from my blog, I have been using NixOS under MacOS for some time now. A lot of numbers and values are displayed when building the flake.

Unfortunately, I hadn't found anything about this in the Nixos documentation. Only a forum post that explained a few figures. So here are the results of my research.

The Screenshot above means the following:

4 Packages are currently building
128 Packages builded
486 total to build

1 file currently in copy progress
1212 files copied
1256 files to copy

4287.8 extracted size copied
4417.9 extracted size

1452.8 downloaded
1477.5 to download

correct me if i am wrong because i did not found a documentation for this output.

link to source: https://discourse.nixos.org/t/nix-build-progress-bar-meaning/28590