Hi @Hopkinslax Assuming you were not connected to your phone's GPS, distance would be calculated as number of steps times stride length. Your stride length should be set to something close, but it is possible it got set way off.
For how to check and adjust stride length, see:
How do I measure and adjust stride length for my Fitbit device?
Note there are separate stride lengths for running and walking.
Welcome to the forums and let us know if that works, or if there is anything else we can help with.