I know a parsec is a distance and not time measurement which is why Han saying in made the run in under 12 parsecs doesn't make sense.
"The thing to keep in mind about Solo's claim of doing the Kessel Run in less than 12 parsecs is that the Kessel Run is through the Maw. Event Horizons around black holes are dependent on the speed at which you are traveling. A standard ship has to do the run in 18 parsecs because to cut the route any closer, the ship would get sucked in. The Falcon, however, is fast enough to straighten the route and cut over 6 parsecs off the distance traveled. This makes sense, since the Falcon is faster than most ships and he was using more power than what the engines should have been able to use. While this argument may all be after-the-fact justification for an actual scriptwriting error, the logic does hold, although Solo could have just been boasting to his potential clients. "