Please Help Me Understand

When I log in to my account, my eat meter says my daily goal is 1600. But I was just looking around the site and clicked on the edit settings and then the "advice" button next to my daily goal. When I went thru the steps again (i didn't change anything), it said I should have 1321 calories a day to make it to my goal. That's a pretty big difference. Could this be the reason that I haven't lost any weight? I'm 5'6, 28 year old female. Please help