[Din] draft-mazieres-dinrg-scp-04 page 15 settting prepared

[Piers Powlesland <[e-mail]>]

Hi,

The segment describing setting "prepared" on page 15 is as follows.

>The highest accepted prepared ballot not exceeding the "ballot"
>field, or NULL if no ballot has been accepted prepared.  Recall
>that ballots with equal counters are totally ordered by the value.
>Hence, if "ballot = <n, x>" and the highest prepared ballot is
>"<n, y>" where "x < y", then the "prepared" field in sent messages
>must be set to "<n-1, y>" instead of "<n, y>", as the latter would
>exceed "ballot".

I am wondering why the prepared counter must be set so that it does
not exceed ballot as opposed to increasing the ballot counter so that
ballot >= prepared?

Also I can't see such a condition in the original SCP whitepaper, and
I'm wondering if I have missed it or if this is a new addition to the
balloting protocol?

Thanks,

Piers