Streaming Replication Protocol and Logical Replication

Hi,

I am writing something to interpret the XLogData messages sent during
logical replication. I want to record the position of the WAL records I
have previously processed so that if I need to restart replication I can
skip to the first WAL record I haven't processed.

If I'm understanding the documentation correctly, adding the 2 values below
will give me the latest byte offset I have processed. So adding 1 to their
sum will tell me where I can start replication.

1. Int64 - The starting point of the WAL data in this message.
2. Byten - A section of the WAL data stream.

So my questions are:
1. Assuming no continuation records, is my understanding above correct?
2. If there are continuation records, do those have the same "starting
point of WAL data in this message" as the main record? If yes, is there
some way to use the protocol to determine when messages are continuations
of each other?

Thank you