Fitbit question

I have this issue too, but I ignore it - trust the mfp numbers rather than the Fitbit when it comes to goal calories. I've found Fitbit to be pretty accurate in general in regards to total daily burn.

I have my Fitbit Flex linked to my MFP acct. I log my food on MFP not Fitbit. I go by MFP as it shows my Fitbit calorie adjustment and gives me a new total for the day.

I have no idea why it does this either, but like others, I totally ignore the Fitbit's opinion on what I ought to eat -- both in if it's telling me I'm over/under, and when it gives me calories to eat on MFP. I just tend to look at the raw numbers. If it says I burnt around 2500 calories, I'll eat accordingly. I'm still in deficit, but the concept works for maintenance as well.

Don't attempt to follow 2 roads to the same destination - it'll be confusing and aggravating, and if a man's driving hope you don't have to ask for directions.

Fitbit for exercise and daily activity goals.
MFP for eating and those goals.

That specific gauge you reference is about useless anyway - remove the tile is usual suggestion.
It is merely a single point in time - right then looking at it - nothing to do with your day as a whole and doesn't help your planning.

The problem with the hitting goal before bed (or before becoming couch potato) and being over goal on first sync in morning is because both MFP and Fitbit are estimating rest of your day as to what you'll burn.
They have no idea when you'll go to bed - so they both estimate a per minute calorie burn which is higher than sleeping.
So it's not until the next morning that Fitbit shares the fact you had no movement for so many hours and only burned so much, and MFP (and Fitbit) lower the prior day's burn, which means the eating goal lowered too. Which you already met.

Good news though - if you always become couch potato or go to bed about the same time, the difference will always be the same, so do the following to know how much to NOT eat.
At that point you stop moving mainly in the evening, notice what the daily eating goal is (not what you ate).
Next morning after first sync, look back at what corrected eating goal is.

That difference is how much you should leave in the green uneaten towards your goal. Then when it lowers next morning - there ya go, met goal.

that being said, I believe there is an option to have them sync constantly (just might use up data...not sure?)

Only using wireless data when connected via WiFi is a device option - not MFP/Fitbit option.

And even if that was the case - Fitbit account is still sending to MFP account (neither of which is on the device) an estimate of daily burn up to that point.

Which doesn't matter if no wireless data is set on device, because you'd never see the results of that action.

But that has nothing to do with MFP/Fitbit - shoot, checking a bank account for recent transaction and not actually have wireless data would be effected too.