Ref Position

Key Ref Position of function Price in Tradable refers to an optional position within the one-dimensional array - if any - associated with the key specified in Target Key
If omitted, 1 is assumed.
If the value associated with the target key is a single scalar element, the entry here is not relevant.
This entry becomes useful if the above value is a one-dimensional array.
In that case, an entry of 1 means that the first element of this array represents the numerical value, which will be perturbed by the root finder solver until it equals the returned fair value that fulfils the desired criteria.
An entry of 2 identifies the second of the array's elements, and so on.

The entries here correspond to those in
Ref Key
This means that if an array of keys is supplied in Ref Key, a similar array of integers must be supplied here.
Then the first integer will correspond to the first key in Ref Key, the second integer will correspond to the second key and so on.