The answer is simple. I have done the distance many times - most of which were on my Calfee with a Garmin 305 Edge. So, I know the exact distance well.

Today, on my new build, I used the timer function on my watch to measure the total time - it was actually 1:03:46 - I rounded up.

I don't have a sister, and I'm probably old enough to be your father, Punk!