Charge 3 distance information inaccurate

[Mummymenace]

I have an aim to walk 3 miles a day. However my main screen on my app doesn't move to completed until I have walked 4 miles. If I change the distance it is always about a mile out. Any ideas to correct it?

Moderator Edit: Clarified subject

[AlejandraFitbit]

Welcome to the Community, @Mummymenace.

Fitbit devices calculate distance based on the device’s accelerometer data and stride length setting.

Default stride length is based on your height and gender. If available, Fitbit devices use GPS data to calculate more precise distances.When you sync your device, our algorithm interprets the data from the device, and you see your distance traveled in the Fitbit app. 

Note that when you track an exercise with GPS, both GPS and accelerometer data are used to calculate the distance shown in the Fitbit app. For more information about accuracy, check the article: How accurate are Fitbit devices?.

Let me know how it goes.