There is a documented process for driving Windchill Find Numbers from a Creo assembly. The issue is that creating an assembly component parameter for every component in the assembly is time consuming and open to human error. Also because it is a parameter created for each component in the assembly you can enter different integer values for each Find Number even though the CAD part is the same. i.e 4 x M6x25 bolt could have 4 different Find Numbers when you only want one driving the Windchill product structure
Solution 1 - At the assembly level allow the start assembly model to contain the component parameter used to drive the Windchill Find Number just like any other part or assembly parameter and ensure that the integer value entered gets used for every instance on the same part in the assembly
Solution 2 - Allow the repeat region report index to be used to drive the Windchill product structure Find Number.
Currently if you have an assembly of 100 parts you need to create the assembly / component parameter 100 times ensuring that you name it the same and that I have. The effort has gone into Windchill but not Creo