5'0 tall weight loss goals and starting points?

5'0" tall here....really glad to see others like on this site....yet I couldn't be more confused!

I would love to lose another 40lbs - currently down 20 (since January of 2012)

I see a personal trainer once a week and workout on my own 4 days a week. My trainer increased my calories to 1800 - which had me on a steady gain for about 2 months, so I dropped it back down to 1300-1500.

I really don't know what my caloric intake should me. I would love it if someone just told me a magic number that seemed to work. MFP tells me 1200, but all research tells me that's too little.

I'm anxious to see where this 1300-1500 caloric intake gets me.

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