Each "volume" (like 008) is dedicated to a single model.
Physical media from this era is degrading. Many titles from the IMOL series have never been officially transferred to digital streaming services due to licensing purgatory or studio closures. As a result, original DVD rips of circulate in private trackers and archive.org collections at a premium. Owning a clean copy is considered a "white whale" for completionists. Imol 008 Hitomi Ogata