23.11 is the nixpkgs/NixOS version. This is the version of the Nix package manager. If you don’t need the newer version then there is nothing to worry about. It doesn’t effect the NixOS and nixpkgs software that you are installing.
This is like an Aptitude package manager update vs Debian version or a Pacman update vs Arch Linux version (not Arch has versions).
23.11 is the nixpkgs/NixOS version. This is the version of the Nix package manager. If you don’t need the newer version then there is nothing to worry about. It doesn’t effect the NixOS and nixpkgs software that you are installing.
This is like an Aptitude package manager update vs Debian version or a Pacman update vs Arch Linux version (not Arch has versions).