Nevermind guys, we were all wrong:
From the script:
Fast ship? You've never heard of the
Should I have?
It's the ship that made the Kessel
run in less than twelve parsecs!
Ben reacts to Solo's stupid attempt to impress them with
In the movie itself, you see a bit of an eyeroll after he says this. Obi-Wan was an educated jedi, having spent his earlier life traversing the galaxy, he probably knows his units. Han either doesn't actually know his units or is just trying to impress the old man. Easy to assume that the eye roll is more "oh, this cocky bastard thinks his ship is fast" but the stage directions make it pretty clear.