The energy of 393 kJ is released as heat. Then, the container will experience an increase of temperature and, given that it is sealed, also an increase of pressure.
The increase of temperature results from the heat developed during the reaction.
The increase of pressure results from the fact that that the solid carbon will become gaseuos carbon dioxide. This gas will occupy a larger volume than the solid carbon and also this elevation of the temperature will make the pressure of the gas inside the container increase.
