Acct-Session-Id

Dear All.

From https://wiki.mikrotik.com/wiki/Manual:RADIUS_Client#Access-Request , there is :

Acct-Session-Id - unique session ID. the first two symbols of session ID represent service (PPP, Hotspot, etc.). The next symbol ...

Is there any documentation about that ‘first two symbols’?

i.e :
Acct-Session-Id = 80f000e0

what ‘80’ mean?
is it PPP? Hotspot? PPPoE? else …

Sincerely
-bino-