I assume you are asking: "When the "total" values are unknown, what is returned
on the notification?" I'm not as IPP-fluent as most are on this mailing list,
but is there a problem with using the out-of-band "unknown" value? If I was
passed a job-impressions value of 0, I would interpret that to mean the job was
going to print 0 impressions.
Or did I misunderstand your question?