יונה ג:ד פירוש: רש״י, Metzudat David ורד״ק

overturned Destroyed. [He did not say, “Destroyed,” because “overturned” has two meanings, bad and good. If they do not repent, it will be destroyed; if they repent, then “overturned” refers to the people of Nineveh, that they will be changed from bad to good, and they will repent. Gloss of Rabbi Akiva(?)]

started out: when he started his way into the city one day's walk, he proclaimed, "There is still forty days' time", and after that Nineveh will be overturned. That is, like the overturning of Sodom and Gemorrah from existence into nothingness.

Jonah started out: The city was three days' journey from one end to the other. Jonah started by entering the city one day's journey. As he walked, he would call out, "Forty days more and Nineveh is overturned!" That is, like the overturning of Sodom and Gemorrah, because their acts were like theirs.