My guess is that you may need to "refresh" your kindle after a synch (via PC or other Android App). I, too have the fitbit app loaded on my Kindle Fire, but it is basically a view only, it doesn't synch from my device (One).
Best Answer
@lisajo2012 wrote:
I do have an app for my Kindle. I can prove it if needed. It works on the android system.
I believe you and I found it. It receives the data via a push from your Fitbit account. That may account for the differences as they may not always be in sync.
As an aside, the Kindle uses a forked version of Android. Amazon took the main Android code and tweaked it for it's own uses, adding some things here and eliminating some things there. That is why not all true Android apps will work on a Kindle, even if you somehow sideload them.