1. The composition X will start cooling and hit the liquidus of An.
2. At this point pure An will start precipitating and the concentration will move along the Liquidus.
3. With further cooling the liquid composition has moved along the liquidus to the eutectic.
4. The liquid remains at eutectic temperature and now begins to crystallize Di along with An, in the proportions corresponding to the composition of the eutectic. 
5. Crystallization of An and Di continues until all of the liquid is used up. With the crystallization of the last droplet of liquid into grains of An and Di, the temperature of the system can now fall below Eutectic temperature.