Green’s Dictionary of Slang

(N.Z. prison) a punishment: seven days solitary confinement, seven days’ Loss of Remission, 28 days Off Privileges.

2001

D. Looser Boobslang [U. Canterbury D.Phil. thesis] 162/2: seven, seven, twenty-eight (also 7 7 28) n. a punishment given to an inmate for repeat offending while in prison (e.g. if he goes up on the same charge more than three times). The punishment involves seven days in the solitary confinement cell, seven days’ Loss of Remission (i.e. seven days added on to the length of an inmate’s sentence) and 28 days Off Privileges.