This is part of the "slave manifest" for the Brig Orleans, which shows a slave called "Plat Hamilton" (line 33). Solomon Northup had been known as Platt while a slave, and one of the men who lured him away from Saratoga Springs, New York, used the last name Hamilton.
The full manifest page has been made available online by the National Archives and Records Administration. You can view it here.
The manifest had a second page. Northup noted that, while the ship was anchored off Norfolk, Virginia, a boat came out to it and more slaves were taken aboard. They are listed on the manifest's second page. One was "Robert Jones," undoubtedly the Robert with whom Northup planned to take over the ship. Northup wrote that Robert died of smallpox while at sea. A note (far right) records the death of Robert: "Examin'd and found Correct with the exception
of Robert Jones who Capt Wickham states died on the Passage."
Some slave manifests have been preserved by the National Archives and Records Administration. For an explanation of what slave manifests are, see this page at Afrigeneas.
Full biography of Solomon Northup, Solomon Northup: The Complete Story of the Author of Twelve Years a Slave.
Information at Solomon Northup page
Solomon Northup was the most well-known kidnapping victim, but he was by no means the only one. The 2016 book, Solomon Northup's Kindred: The Kidnapping of Free Citizens before the Civil War, tells about many others who were kidnapped and sold into slavery. The book also provides historical background that explains why kidnappers were able to operate with relative ease.