Probably ran the casters on a conveyor belt/treadmill for whatever length of time.
At a speed of 3.5 mph, youd only have to run the treadmill for about 12 days to get 10,000 miles. There are testing facilities that you can hire for this.
Or its all made up.
SpruceBringsteen@lemmy.world 6 days ago
You can continue testing something after you break it.