Update file EN-304-624.md

### C.1.1 Riks levels calculation

To calculate the risk we use the following tables, where in the matrix presented in Figure C.1.1-3, we defini how the impact (Figure C.1.1-1) and likelyhood (Figure C.1.1-2) associated to a risk are combine to calcute the final risk value.

Later on in sections C.1.2 and C.1.3 we further define for the different use cases the impact factors to define these likelihood and impact values.

As a remainder the 4 use cases define in the standard are:

- UC1:	Private PKI for none critical entities

- UC2:	Private PKI for critical entities

- UC3:	Public CA PKI software

- UC4:	C-ITS PKI

![Figure C.1.1-1: Impact scale](media/ImpactScale.png)