Use this property to specify the position an OPC UA Block Element occupies among the Elements configured by the Size property of the OPC UA Block Tag in which it is inserted. This property accepts values from 0 (zero) to a number less than the value defined in Size. For example, when configuring an OPC UA Block Tag with its Size property equal to 20, the maximum valid number for the Index property is 19 and the minimum is 0 (zero). This property can be changed after communication starts. Default value of this property is 0 (zero), but when mapping Elements of an OPC UA Block Tag, E3 Studio automatically configures the Index property to a value according to the specified.