India GST localization: Cat code set up

The link between the GST Category Type Setup and the account/item cat codes is not clear.   The P75I806 uses UDC 75I / CY for HSN and SAC codes. The P75I809 (Item Attributes/Category Codes) to link SAC and HSN codes
to cat codes , e.g. 16, 17.  What are these cat codes?  There is no link to a UDC to indicate what these are.

I am looking for a link between the SAC codes and the service accounts that the code relates to.  Similarly, I am looking for the link between the HSN code and the inventory items that the code corresponds with.