I have an ITRA ranking of 495 ( https://itra.run/community/david.stuart/646114// ). You can find yours here ( https://itra.run/community/ ). An explanation of the rankings are here: http://76thmile.blogspot.com/2017/02/hardest-itra-races-why-killians-2241.html
Back when I reverse engineered the ITRA rankings, I predicted a UTMB finish time of 39 hours based on my ranking (it was 489 back then).
I pulled out the rankings for roughly 100 finishers of the 2018 UTMB. I looked at the XL ranking because a) The 2018 UTMB would be included in the XXL ranking so the prediction would be somewhat circular b) I don't have an XXL ranking
Ranking is reasonable predictive but with quite a lot of variance. The ITRA predictions are pretty good but there are quite a few highly ranked runners who finished much slower than predicted.