It's sort of unclear. Instead of going into too much detail about narrative accounts of Mar's actions, this book comes at it slantwise, looking at his policies and the growth of the city and associated country.
Specific laws and policies attributed to Mar include universal military service for people between twenty-two and twenty-four who couldn't prove health or financial hardship; exile and seizure of assets for rape and murder; the recently-suspended policy that resembles habeas corpus; jury trials, semi-voluntary for the jurors; money and food aid for pregnant people, all children under five, and children between five and ten actively attending school; and the election of an advisory council.
It's possible to infer a lower bound for tax revenue based on the number of person-hours of labor that went into the shield wall and the eco grid, both public works attributed to Mar, and given the amount of time those took to complete and the published tax rates (where those are still available), it's possible to put a lower bound on the mean population despite the lack of a census. That plus other records make it possible to guess the population growth rate, and it's particularly impressive given that they were actively subject to attempted genocide the entire time. Of course, part of it isn't from people being born. By all accounts they put a lot of effort into facilitating migration and trade between different settlements, and Haven City and its associated country seem to have gotten a lot of net immigration.
Another notable thing about Mar's reign is that, while it's remembered extremely fondly now, published works from the time, including newspaper editorials (something that only began to come into existence about halfway through his reign), included a lot of criticism of him and his policies.
It's possible to date the construction of nearly every large statue of or monument to him, and they all post-date his reign, with exactly one exception: his tomb was almost entirely completed in his lifetime.
There are not only no statues of him from during his reign, there are also no reliable contemporary depictions of Mar. Samos has a pet theory that Mar isn't even one person, but several working together under a shared pseudonym. Not just because his face isn't reliably known; also because he handled a lot of governance himself, at the same time as he directed the war against the metal heads, at the same time as he designed and organized the building of the shield wall and the eco grid and the sewer system and the tomb, at the same time as he collected and wrote commentaries on surviving samples of Precursor writing, at the same time as he apparently had a family, at the same time as he wrote an impassioned treatise on the concept of human rights, at the same time as he negotiated peace and mutual protection with the lurkers of Misty Island, at the same time as he wrote half a book on astronomy and two contradictory books on the philosophy of governance. It's also possible there was a Mar, but that other people's achievements ended up attributed to him somehow, whether because he deliberately stole the credit or just because of the unreliability of the historical record.
If this were true, the narrative of Mar as one person who appeared one day and won his victories through his personal valor and strength of character would be thoroughly ungrounded.
It's not a terribly long book.
While he's reading, Rit leaves, and someone stops by to pick up some of the food.