Determining Goal Weight

I'm just curious to know how/why you determined your goal weight.

I've heard "it's what I weighed in high school" or "before my pregnancy" - but I was not a healthy weight in high school and was about 50lbs less than I am now. I'm now in a healthy BMI range, but would love to be even lower. I can still drop another 13lbs to be in a healthy range.

I'm just confused when I see people my height wanting to be at a goal weight and wanting to be at what my starting weight was. I see justifications like "I'm big boned" etc etc. I simply don't see myself as thin or fit yet. I still see excess body fat, I'm within 5-7lbs of my "goal" weight but am the same size clothing as I was when I was at that weight before.

Or another example, my best friend is VERY small, she's tiny and she was amazed that I am the same size pants as she is - because she is very small. I don't "look" that small yet, even to other people. Or they are amazed when I say what my pants size is, because "you dont look it". I know that 5-7 lbs won't really be much of a size change at this point. Ideally, I'd like to just look like I have muscle vs fat.

I'm wondering if my goal weight is realistic. I know if I lost the additional weight to put me at the bottom of the BMI scale I would be a smaller size, it's about 13lbs more, but would I "look" thin then?