C. Remission of sentence
Under section 69(1) of the Prison Rules (Cap. 234A), a prisoner serving a sentence of imprisonment for an actual term of more than 1 month may, on the ground of his industry and good conduct, be granted remission provided that this rule shall not permit the reduction of the actual term to less than 31 days.
Further, under section 69(2) of the Prison Rules (Cap. 234A), the remission granted under this rule shall not exceed one-third of the total of the actual term and any period spent in custody taken into account under section 67A of the Criminal Procedure Ordinance (Cap. 221), which allows a reduction of a sentence of imprisonment to take into account any period spent in custody prior to sentencing.
For example, if the court rules that the starting point of the imprisonment sentence to be imposed on a defendant should be 9 months, normally the defendant will be entitled to a 1/3 discount if he pleads guilty at the earliest opportunity. Then if the defendant behaves in prison, he will have another 1/3 discount. In other words, he only needs to serve 4 months in prison (9 months x 2/3 x 2/3).