This situation arises quite often. The course is a single loop with no turn-around and the RD would like the start and finish to be in the same place. Or there is a 5k and a 10k and the RD wants the start for both to be in the same place and the finish for both to be in the same place.
When the course is measured with these desired start and finish locations, it comes out to be 5003 meters. I think most agree it's okay to have 5k in the name of race on the map and to certify it as 5000 meters. But what's the limit on this? If the distance came out to be 5075 meters I think most would agree we shouldn't certify it as being 5000 meters. It sounds like Bob believes that limit should be 2xSCPF. So for a 5k, if the measured distance is 5011 meters, the course length on the certificate would be 5011 meters.
The "zzz" is about the name of the course on the map. I think most would agree that if the measured distance came out to be 6100 meters, we shouldn't allow "5k" to be part of the name of the course on the certification map. USATF and RRTC will look pretty ridiculous if have cert maps out there that say Joe's 5k, course distance: 6100 meters. But what's the limit on that? A course that is 5011 meters should have it's distance listed as 5011 meters, but do we still allow "5k" in the course name? My opinion is that's okay. But what if the measured distance is 5050 meters?
So xxx is the amount we allow the measured distance of the course to be over 5000 meters and still call the certified distance 5000 meters.
And zzz is the amount we allow the measured distance of the course to be over 5000 meters and still allow "5k" to be in the course name on the map (even though the actual measured distance is listed on the certificate).