Through plan and exercise, I have lost almost 5 pounds this week. Is this safe?

I have been watching my calories, and usually eat much less than 600 a day after calculating calories burned from exercise. Today, I ended up with ~334 Calories. I'm not looking for what I should be consuming, I already know a female should consume a minimum of 1,200 Calories. However, I can not ever imagine eating that many. I am female, 16 years of age, 5'5, currently 168 pounds. Thank you for any feedback received in advance.
Asked May 31, 2014

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