Calories sync between mapmywalk and mfp

goodwifey82

I updated Mfp today. After a nearly 4mile walk his evening Mmw calculated a 634cal burn. Normally when this workout is synced to Mfp the calories are the same. I know they are probably pretty generous but I log to keep track of my exercise for the day.
Today when I logged, Mfp is.only recording calories as 273. That's a big difference from the Mmw app. Is this to do with the update. Are they just becoming more realistic with there calorie burns now?