Yes, info in several recent threads.

Separate Fitbit telling MFP steps and calorie burn - not related on MFP at all, merely 2 stats, former for viewing, latter for adjusting eating goal.

The calorie adjustment may be put under Exercise diary for handling it correctly for eating level, but it's the difference between what Fitbit calculates you burned in total for the day, compared to what MFP thought you'd burn without exercise by your selection of activity level (sedentary, lightly active, ect).
It could be NO exercise and just increased daily activity, it could be exercise and extra lazy that day.

Step-based exercise you do not need to enter, unless walking or running was decent time with decent incline that Fitbit would have no idea about increased calorie burn on.
Any non-step based exercise should be manually logged - swimming should be obvious, rowing, biking, lifting, elliptical, ect.

So NEVER compare the calorie adjustment to the exercise burn, as that's not what it is and likely should never match anyway.
But use the HRM for correct steady-state aerobic cardio that you do. Not for lifting or intervals or non-steady-state HR which is incorrect usage of formula that calculates calorie burn. It'll be inflated.
Use the database entries for Weight lifting on Fitbit, or Strength Training on MFP.

How do I sync MFB and MFP together? I can not find the original How to get started discussion thread.