"So much." Harry leaned into his mother's touch, and he noticed when she paused at the scar on his forehead.
He began with the same story he told Sirius. He explained how Pettigrew had betrayed their family, how he framed Sirius for a mass murder, and how Sirius landed in Azkaban for several years.
He then told his mum about how he had lived with Vernon and Petunia for ten years. He willingly admitted that they were no surrogate parents anyone would want for their children, but he left out the abuse, and the cupboard under the stairs. He didn't mention the chores he was forced to do, the cooking and the cleaning, the weeding and the mowing, but he did tell Lily that he had been ready for Hogwarts, and surprised about being a wizard.
Harry left out the first two years of school, those were stories he had told James. Well, the watered down version, lacking any narrow escapes, and visits to the hospital. But he did tell the true story of how he saved Sirius Black from dementors, and Voldemort's rebirth. And he told her about how he got Sirius killed, two years after he had been freed.
He gave a passing mention to most of the events of the last war. It was something he still rarely spoke about. He mentioned the Horcrux hunt, and mentioned killing Voldemort, but he didn't bring up how Voldemort had to kill him first.
After he finished telling the story, his water was gone, and he sat playing with the glass in his hand. He waited for a reaction.