He wasn't sentenced to that, it must be an error in the report. He was sentenced to an indeterminate sentence with a minimum of three years. That means he's in jail (and presumably being psychologically assessed/getting treatment) for at least three years, then someone has to decide if he's safe or not. if he's not safe, he stays in jail and gets a review(I think) once a year. This will continue until he's 'cured' or he dies, whichever comes first. Given the obvious state of psychosis he's in, frankly I think it's pretty unlikely he'll ever see the outside world again.
Having said that, whoever came up with the first sentence deserves to be put in some stocks in Piccadilly Gardens and left there for a few weeks. A community service order? For sexual assault against a child? WTF?
Jon