I just finished a 6.3km run that lasted about 0hh:42mm:0ss !
I did the no-thinking Stag Hill route. I have a good record that it's 6.3k and my best guess is that it took me 42 minutes. My legs are a bit sore so it might have been faster but the one thing I do know is that I'm not good at estimating anything about running statistics - which is why I have an app to do it for me. Nonetheless, doesn't insist that I upload a GPS file as proof (even though it's good to have, so here I am, staking my claim to another few miles to get me on the leaderboard.
Check out some detailed info at my EXHAUST page
Join me in testing out EXHAUST!