In reply to fxceltic:
It's equivalent to a "normal" sentence of 16 years. As it was a guilty plea he will have received a discount of between 1/5 to 1/3 - so probably equivalent to a sentence of 20 to 24 years.
He has to serve 8 but then he has to convince a parole board that he no longer poses a risk. If he fails to convince them - he stays in for the rest of the year till his next chance.
A normal sentence would mean he walks out after serving half.