fitbit calorie adjustment

trying to get used to my fitbit in regards to extra calories to eat etc.. first of all it reckons I only burn 200 extra calories while I work a 12 hour shift in a busy nursing home, but it obviously doesn't know I'm on a calorie deficit from MFP. If i put in 3 hours slow walking in the cardio exercise it says I burn about 500 calories.

Today because I haven't worn my fitbit its taken 160 calories off my daily calorie allowance, I'm only on 1360 cals per day as it is so now i have 1200 calories for the day!!! Shall I just eat the extra 160 calories anyway??

Any advice??