Only 30 days in jail?

3 men snuck into a the bedroom of a friend's mom and sexually assaulted her. One of those men will spend 30 days in jail and be registered as a sex offender. The other two won't. That's terrible that that's the worst punishment they are receiving. I feel like it should be worse, because others might see that its not such a bad punishment and do it too. I don't feel safe.