Lap time not correct?

I am playing endurance gt on the story mode and just did 20 laps of spa, in the r835 class and i set a 1:21:4 and it then when the race finished it makes it 1:23 into the leaderboards? why?? they were mostly all clean laps, no asterisks and only a couple rewinds.
update:
strange maybe in story races? there is no dirty warning? i can go all over the track and no indication it was dirty yet in multiplayer there is always a indicator that pops up when going dirty next to the time.