What specific data should be inserted in place of X in the equation provided below to calculate risk severity?
(Risk severity = X*Impact)

The specific data that should be inserted in place of X is the likelihood of occurrence of the risk event. This value typically ranges from 0 to 1, where 0 represents no likelihood of occurrence and 1 represents a high likelihood of occurrence.
For example, if the likelihood of occurrence is determined to be 0.8 (80%), you would substitute X with 0.8 in the equation to calculate the risk severity:
Risk severity = 0.8 * Impact
Please note that Impact is another factor that needs to be defined and assigned a value to calculate the risk severity accurately.