As a child, Rahel wears a toy wristwatch:
[The wristwatch] had the time painted on it. Ten to two. One of her ambitions was to own a watch on which she could change the time whenever she wanted to (which according to her what Time was meant for in the first place). (2.12)
So every time Rahel looks at her watch, it's ten minutes to two. Big deal, right? Well, let's think a little deeper and consider the role time plays in the novel. For one thing, it doesn't always work the way we expect it to. Like Rahel and Estha, we experience the present and past almost simultaneously. But when we're in the past, we're in a very specific two-week period, and in the present we're in a very specific span of just a couple of days.
Unlike most other novels that start at one point and move forward through time at a normal pace, The God of Small Things is, for the most part, frozen in time. We get a little bit of filler information about what happened to Rahel as a young woman, but we don't live through those experiences with her. By the same token, we really never find out what happens in Estha's life in the 23 years that pass between the day he is Returned to Baba and the day he comes back to Ayemenem.
Just as Rahel's watch has "stopped" permanently and always displays the exact same time, so are the events in the novel frozen. Rahel's watch, then, can be viewed as a symbol of how one brief moment in her life – the days surrounding Sophie Mol's death – was in a way the only time that mattered.