Confused about BMR, TDEE and daily limit

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Hi guys,
Hoping for someone to give me what calorie figure I should be eating at!

I've got two numbers for my BMR - one of 1557, and the other of 1717.
My TDEE is 1859.
I live a fairly sedentary life and log all my exercise/walks.

When I signed up to MFP - it calculated a figure of 1200 calories per day. And I ate at 1200 for the first week, and lost weight. But for the next week I ate slightly over, but didn't lose anything - gained what I had lost in fact!

So this has left me confused - should I stick at 1200 or up it to 1600 or so?

Feel free to add me :)