Currently, there's no easy way to get the size of the impending
download. Skopeo doesn't offer the size of the OCI image [1] and it's
debatable whether another 23 MB binary ought to be pulled in as a
dependency just for this.
Given that the default fedora-toolbox images are the only base images
available via a public repository, the size of the download is hard
coded to reflect the approximate size of the fedora-toolbox images.
These images are between 451 MB and 483 MB, so 500 MB should be a
reasonably suggestive approximate that shouldn't negatively surprise
users.
[1] https://github.com/containers/skopeo/issues/641https://github.com/debarshiray/toolbox/issues/134
