It would not surprise me one bit if your number of three was correct. The prisons are a for "profit" business and they make more money by keeping them at capacity or damn near capacity. People don't realize either just how many people are in prison that never did commit a crime.
Prosecutors file charges all the time so that they can scare people with lengthy potential sentences and that get them to plead guilty to a "lessor" offense with a shorter sentence where they will be out in a year or two, where as if they went to trial and got convicted of the higher charges they would be facing 15 to 20 years behind bars.
Couple that with those people have probably been sitting in the county jail for 4 or 6 months because they can't make bail, so the reality is that counts as "prison" time and they spend 8 more months in the state run prison before they can get out.
People have this happen all the time, most would rather give up two years than gamble on losing twenty, even though they didn't do a damn thing wrong.
It is sickening the things that go on in "the justice" system.