But what if no time was mentioned? Just community service. Would they extend the time?

Also, what if the person had extreme mental problems, and we had mental hospital records to prove that?

There may be defenses and the prosecution might not want to send the person back to jail at all. What I was saying is that any violation can result in being sentenced to the remaining time. It does not mean that it will. "lesser" violations do not necessarily cary lesser penalties for probation purposes, staying out after curfew for example can result in years behind bars under some circumstances.