Numbers Game

As Jack Straw looks desperately for a way out of the prison crisis (one that is mostly of the Government's making) there is talk of extending the early release scheme to free a few more spaces. So here are the numbers as they stand today:
Maximum sentence available to magistrates: 6 months. Let's call that 180 days. Defendant pleads guilty (most do) so one-third reduction. That's 120 days. That is automatically reduced by half, leaving 60 days. Current early release is 18 days, leaving 42 days to serve. That's six weeks. Prisons don't release at weekends or on bank holidays, so those with sentences expiring then are released the previous Friday, possibly knocking 2 more days off the sentence. If, as suggested in the press, early release is extended to 30 days, then the most that magistrates can hand down will be effectively 28 to 30 days - roughly four weeks. Hardly Judge Jeffreys is it?