However, take our global population today, and a post-revolutionary situation could see even a million real convicts in such a Gulag system. This figure is less than the 2+ million incarcerated in the US prison system, and far less than the "Gulag atrocities," but it's more than enough to commit to Gulag projects here and there.
The balance between Group A (serial murderers, serious counterrevolutionaries, class enemies, grossly corrupt officials, etc.) and Group B (criminal offenses punishable today by short- or medium-term "community service," including criminal graffiti) would tilt towards Group B over time, but like I said, even a million people from both groups would be more than enough. Note: both groups would have high turnover, with Group A's turnover being due mainly to death, and Group B's turnover being due to paroles after sentences have been served.