Charge 3 steps and miles accuracy concern

[SunsetRunner]

Yesterday I walked 8 miles, my overall daily step count was just over 20,000...my Fitbit tracking (through GPS) told me that I walked 10 miles. When it synced with my app then it changed my step count to over 23,000.
I was in several challenges, one of which showed 20,000 steps but the other 3 showed around 17,000.  
My friend walked 5 miles today but it gave her 22,500 steps, that’s over double the amount it should be.  I’m not sure what is going on but it is EXTREMELY aggravating.  It makes me not trust my Charge 3.  It makes my friend not trust her Inspire.  
(I did try pretty much everything EXCEPT doing a Factory Reset to attempt to get it to work properly—also my iPhone 11 Pro as well as my Fitbit have the most current updates)

Moderator edit: subject for clarity

[LiliyaFitbit]

Welcome to the Fitbit Community, @SunsetRunner.

I appreciate your participation in the Forums and sharing your concern about your Charge 3 tracking your steps and distance accurately. Thank you for your troubleshooting efforts, I totally understand how you are feeling and I am here to help. I appreciate the additional details and would like to advise that Fitbit devices are personalized to each user's personal information and you can see the difference if you compare your friend's data with yours. If you feel that your step count and distance are inaccurate, confirm the following are correct in the Fitbit app:

• Your wrist settings (For more information, see Does the wrist I wear my device on affect accuracy?)
• Your height (For more information, see How do I manage my Fitbit profile?)

For more information, see What can I do if my step count seems inaccurate?

Thank you for mentioning that you tracked your activity through GPS. GPS accuracy depends on the signal strength among other factors. A weak GPS signal might affect the accuracy of your route and other activity data. I recommend checking out this article for more information.

Regarding your concern with your step total on challenges, I recommend checking these possible reasons for this issue: 

1. Your steps have fully synced to our database but you're not viewing the mobile app dashboard in Live Data Mode. (Live data mode would show the word "connected" under your tracker tile). 

2. You used MobileRun to track GPS data with your app. Only steps recorded by a tracker or MobileTrack are counted toward challenges.

3. All challenge participants are not in the same time zone. The challenge begins and ends in the challenge owner's time zone, so if you're in a different time zone than the challenge owner, you may notice that your challenge leaderboard stats do not always match your dashboard stats.

For more information, see our information about challenges here. 

Keep me posted on the outcome. I'll be around if you have any additional questions.