The article explores the process of development and application of the injunction of the Inter-American Court of Human Rights that established the different calculation of the penalty for prisoners allocated at the Instituto Penal Plácido de Sá Carvalho, in Rio de Janeiro. According to the determinations of that court, due to the deteriorating conditions of confinement that prevail in that prison, each day of sentence served there will count as two. Central to this work is the hypothesis that this exceptional situation can reveal deep and implicit meanings that punishment and imprisonment assume in our context. In addition, the present analysis aims to provide elements for the improvement of the decarceration policies, as well as for the prevention of torture.