The answer is: The evidence details how Gandhi saw a man who had been beaten and knew that the man could not leave.
Gandhi was well aware of the indentured servants' brutal treatment and he compares it with his previous situation in India, where he couldn't leave his society since, if he crossed the blackwater, he would lose caste.
Later, Gandhi encounters a man in terrible conditions, as a result of his work. Gandhi knew that something similar happened to the indentured labourer: they could not leave their jobs because they were "property of his master" and, if they ever tried so, they would be prosecuted and jailed.
