It's pretty easy to determine miles by using the SP fitness tracker. Go to it, then scroll down to "Mileage". There's a tab next to it that reads "Map Route" . Click on that and you can enter the exact route you biked and it will give you miles. I use it for walking/ hiking/biking - once a route is entered, you can save it and do a 1-click enter when you repeat that same trip.
Shoot for the moon. Even if you miss you will land amongst the stars.
Nothing changes when nothing changes.