Thanks for sharing this tool to help cleanup the Git history. Please be aware that it will rewrite the history, which could be very impactful to existing branches, merge requests and local clones. A similar approach is described in the documentation: https://docs.gitlab.com/ee/user/project/repository/reducing_...
Also my team's biggest repo is a 2.5 GB checkout but gitlab (self-managed) reports it as 185MB "files" and 353 MB "storage" (no CI/CD artifacts).