Regarding Secure Data Hubs specification

Hi Manu and Whole W3c Team,

I am currently reading the document related to Service hubs which is
discussing the pointed which should be taken into consideration while
developing a service hub.

I am not able to understand a few points.
Could you please help me?

In Data hub configuration section
there is a Point called
sequence A unique counter for the data hub in order to ensure that clients
are properly synchronized to the data hub. The value is required and *MUST* be
an unsigned 64-bit number.

I am not able to understand this point.


And another question is
what are
kek.id
kek.type
hmac.id
hmac.type.

I am actually not aware of these types of keys and ids.


Regards
Sethi Shivam