The Engine give Wrong FPS Information?

Hey i have an Question, I have an Strange bug on Ue4,

The STAT FPS Command shows me Like 50 FPS, and the Afterburner Inidicator or the NVDIA Shadow Play FPS Indicator shows me x2 of them

So when the Engine shows me 40- on Afterburner i have 80 , Why?

is this a BUG?

Have an 1070

here are Pictures:

Hope a Staff Member can give me an Answer so i can Solve this

Thanks for your Time

~KS