Value

Key Value in Valuation refers to the value assigned to the Quotable object entered in Quotable as of the date specified in Trade Date
It is expected to be an object of type Probability Measure
In most cases its type will equal the Probability Measure's subtype Exact Number, in which case it will appear to the user interface as a regular number for simplicity purposes.

Look at Quotable for more details on what this value represents.