Property is indexed. Possible indexes are from 1 to 10.

Using this project property, you can define up to ten tables for replacement texts (via the index). You can use these tables to replace the values of block properties: When editing block properties you can use the dialog Format: Block property to select the table with the replacement texts to be used for a property. The values of the selected property are then compared to the texts defined in the table and replaced accordingly.

Reference

ProjectPropertyList Class
ProjectPropertyList Members