It's not perfect by any means but as far as I know, this is the first and only run of it's kind in Halo: Reach, making it the de-facto World Record.
The time given is based on actual time spent in-game from the begining of Winter Contingency to the end of Pillar of Autumn. 'Lone Wolf' is a bonus level and can be ended in a few seconds by attempting grenade-suicide and so was not counted for timing the run. Level times were worked out using the time-bar on the saved films played back through theatre - the same method as 'LASO' or 'Mythic' runs use. Then all the level times were added up to get the total for the whole game.