Fitbit query??

KirstyMoo11

Hi there,
I have recently invested in a Fitbit Flex and I'm a little confused!
I tracked my fitness did today of 45 minutes of exercise!
Obviously my Fitbit records my steps during the exercise and adds them in....is this then doubling my calories burned?
The fitness did is more than steps of course....but am I double logging now?

Hope this makes sense!