Steps per Miles varies from day to day. How is that possible?

[Timjs63]

HR5 on one day have 13,184 steps for 6.59 Miles per the device/app. then on a subsequent day have 13,920 steps for only 6.53 Miles. Nearly 800 more steps but less Miles... 

[RiekoC]

Hello @Timjs63 

Wrist worn fitness trackers, including Fitbits, use accelerometers & arm movement to track steps. As a result, your Fitbit will track steps based on arm movement, even though you haven't traveled any distance. For example, I will see steps tracked when I fold laundry.

It could be that on the day where you have 800 more steps but less miles, you had a lot more arm movement without actually taking steps.