Property is indexed. Possible indexes are from 1 to 50.

Subset of a part, e.g. 5 pieces of a part, which are only provided in conduits of up to 100. At parts for cables, connections and their accessories (for example shrink tubes or insulating tubes) the contents of this property is evaluated as a length and the entry of decimal values is possible, for example "0.7 m". The value entered here is synchronized with the cable length (Length field in the Cable tab of the property dialog) for the main part of a cable. Using the index, you can differentiate between 50 entries.

Reference

FunctionPropertyList Class
FunctionPropertyList Members