Theoretically he could have been convicted a few times (probably on a plea deal) and done a few months or years, but it suggests that he was indeed arrested many more times than he was convicted because no one serves 20 prison sentences by the age of 30.

It's a super common tactic among people who vilify the homeless to suggest all arrests or even most have even the slimmest bit of legitimacy rather than cops just bullying vulnerable people who live near where a crime happened before releasing them on dropped charges.