Winston recalls playing a game, Snakes and Ladders, with his mother. How excited and happy he had been, shouting with laughter.
He recalled how the tiddly-winks climbed hopefully up the ladders and then came slithering down the snakes again, almost to the starting-point.
He and his mother played eight games, winning four each.
His tiny sister, too young to understand what the game was about, had sat propped up against a bolster, laughing because her mother and brother were laughing. For a whole afternoon they had all been happy together.
Then Winston pushed the picture out of his mind labelling it a false memory.
Although it is easy to shrug though this portion of the chapter, the import is that everything in his life that had meaning or made him happy was erased by the Party. And that a stray memory that escape, would be captured and erased by Winston himself.