Property is indexed. Possible indexes are from 1 to 16.

The transformation point is used as the base point for rotation and flipping. Each symbol variant can have its own transformation point; symbol variants are distinguished via the index. The transformation point is entered as a coordinate in mm, e.g., "2.0/2.0". The entry refers to the insertion point of the respective symbol variant. If a transformation point has not been defined for a symbol variant, the first connection point of the symbol will be used as a base point.

Reference

SymbolPropertyList Class
SymbolPropertyList Members