The Relationship Between Capitalists and Workers

The capitalist is able to extract surplus value from the worker. In an eight hour, eight hour work day, four hours might be spent on necessary labor, four hours spent on surplus labor. If we were to increase that work day by, lets say, two hours, to make it ten hours, still assuming wages todo the same in eve, i four hours are spent for the worker to earn that money in order to live. But then that is extended out over ten hours, which means that six hours is spent exploiting the worker, instead of four previously.