A Nerd Moment: the boast Solo makes about the Falcon making a run in so many parsecs — a measurement of distance rather than time — is explained in Star Wars canon that hyperspace travel is not in a straight line, but hyperspace routes follow convoluted paths to avoid things like gravity wells. So taking a shorter route than others is bragging, for shorter is not only faster it speaks of superior navigational skill and special knowledge.
The joke is that it is not Han or even entirely the Falcon that makes this possible but Chewie whom we are elsewhere told was a member of a secretive Wookie navigation guild which had mapped out routes unknown to many, even unknown to the Jedi. This presumably my account for C3P0 commenting that the navigation computer has a very unusual accent.
This has been a Nerd Moment.
Now that you mention it, I vaguely remember someone saying that making the Kessel run in parsecs was a goof. Thanks for the deeper explanation!