This is the Linda Brent Show. From the very first page, with the subtitle "Written by Herself," Jacobs highlights that her account is personal and true. She uses "I" throughout, and she doesn't provide any information that she couldn't personally have known. No insights into Dr. Flint's motivations; no clues about what Aunt Martha is thinking, or at least not any that Linda doesn't come up with herself.
At the same time, her narrator is retrospective. Jacobs creates a character to play herself, and she looks back on her life to offer interpretation and reflection. This lets her foreshadow what will happen, as when she writes, “Those were happy days—too happy to last” (1.3). At other moments, she's able to correct false information. At one point, Linda recalls a slaveholder telling her that one of her friends was miserable up north. From her position in the present, she writes, “This whole story was false. I afterwards staid with that friend in New York, and found her in comfortable circumstances” (8.2).
What this does is kind of cool: we have a first-person narrator, but it's almost as though she's telling someone else's story—because in a way, she is. Sure, most of these incidents happened to Jacobs. But she's crafting into a skillful narrative that turns Linda, not Jacobs, into an archetypal figure of female slavery.