It was a marketing gag without substance. The real number is 4500 steps through 7500 steps for improving benefit, but not so good outside that range in either direction.
That is actually good to know as it tells us that the longer distances will likely serve to diminish you beyond normal recovery. Thus pounding out 10 K paces per day may induce persistent wear that will need a break. fortunately we seem to do just that thanks to weekends.
It all comes down to doing two to four miles of actual walking to get the full benefit and likely once a week is ample as well. This will expand as you feel like it into other days..