We didn't do any extensive optimization and didn't check system requirements since this game was made in a 48-hour game jam. The game uses a lot of dynamic lighting on Unreal Engine 4 and currently has no in-game options menu to tweak performance. I hope this can give you enough reference points for system requirements based on your experience.
We're working on a new version of The Butler, and we'll be making sure to have better in-game options and a better idea of system requirements.
Hope this helps