I think they got their numbers wrong. From 3000:1 to 5000:1 is a change of 1.6:1 not 3000:1 which would be a bit extreme. Maby it would be clearer if they simply used normal photographic jargon, ie f-stops, instead of trying to develop new math. That would make it an increase of two thirds of a stop. Still a total of over 12 stops is impressive.