Confused by rpc IDs in MSCallGraph data of cluster-trace-microservices-v2021

Hi, I am very confused as to how the rpc ids are encoded in the CallGraph data.
From the readme of the trace-data, "rpcID 0.1.1 and 0.1.2 denote two calls that two different DMs are called by the same UM, which is the DM in the call with rpcID 0.1"
However, I am not sure how to figure out the UM rpc ID and DM rpc ID from the given data in the .csv files.

Here is an example of an rpcID from the dataset: "0.1.3.1.1.1.12". How can I extract the UM rpcID and DM rpcID from this?
Any help would be appreciated! Thanks.

Read the trace-data README alongside the MSCallGraph CSV files, starting with the rpcID examples and the referenced UM/DM relationship. Done means documenting how an rpcID such as 0.1.3.1.1.1.12 maps to its UM and DM IDs, with a concrete explanation grounded in the dataset.

Written by the indexing model from the issue text.