I recently ran a team Roshan Kill run, and we killed Rosh 40 Seconds before Creeps spawned. Currently there is no way to notate runs with negative in game time, as putting our in game as 40 seconds would imply that the run took a minute longer than it did. Currently my only option is to leave in game time blank which doesn't seem like a great solution since in game time is what seems to have priority, so our run would be ranked lower than the run which took 3 more minutes than ours.
Last time i ran TRK, i've submitted IGT "as is" (so, 0:57 - 0:56 etc), but did RTA calculations myself. https://docs.google.com/spreadsheets/d/1m0bjfuSuxLjqs9XylkVdPnOj3Hhu2OrKLgjiLdf7lKE/edit#gid=868932706
Therefore, you can submit it as 0:40 IGT / x:xx RTA, as the lb's are being timed by RTA atm.
upd: IGT was necessary, because i thought that it would attract more peeps into running Dota, but i was wrong. Kind of.
The 7.35 update brings a lot of changes to heroes, items, and even the map. We've decided it warrants a full Legacy move once again, as per usual. Good luck to people running in the new patch!