Confused - advice appreciated: how much should I be eating?

I've done a lot of reading around the site and different places and for the last few weeks I've been following the amount of calories CC recommended, but I'd like to make sure I'm getting it right.

I'm 20, female, about 5'9, small frame, pretty sedentry by CC's definitions, 150lbs, want to be back down to my weight of about a year ago which was 132lbs (before a boat load of stress and life happenings). CC says the goal is August 1st and put me on 1300 calories a day.

ETA: I'm also a vegetarian.

My question is: is this too little? This site says my BMR is 1537.8, which multiplied by their sedentry number of 1.2 gives me 1845.36, and so if I understand everything I've read correctly, 1300 isn't too little as it's roughly a 500 calorie defecit. Do I understand correctly?

Today I burnt 200 or so calories walking, and my little burn meter says the total estimate for today is 1940 burnt calories which leaves me with about a 700 defecit. There have been a few days where I've had to do lots of walking about and have burnt significantly more those days, so should I therefore have eaten more to keep it at a 500 defecit so as not to muck up my metabolism?

Sorry for the long winded question, I'd just like to get it right. I do intend to add exercise in (it takes 21 days to make a habit so I'm told, so tracking and keeping on top of my eating was my first step, drinking more water is my next step and then exercise when I'm not under so much pressure at uni). I understand how important exercise is to weight loss and to be honest I'd rather tone up and be healthy than just lose the weight, hence the steps and trying to understand how to be healthy better - lifestyle change not just a fad :)

Anyway, so once I do start exercising, I assume that one would change their activity level up and this would then recommend a different calorie intake to make up for the defecit? And in relation to my last question, on days you do more should you eat more to keep the defecit the same, or is that really counterproductive? Which is how it sounds in my head.

Thanks in advance :)

I'd always start slightly higher and work down if necessary.  At your stats 1400-1500 should be enough to allow you to lose weight.  Chances are you're not as sedentary as you think.  If you make up the total with healthy foods and drink plenty of water you'll also lose fluid-weight.  If you add in a little gentle exercise (20 - 30 min walk each day would be enough ) then you'd definitely lose steadily every week.

Once you start exercising more regularly or more strenuously change the activity level and see what it looks like.  I think changing your food every day based on what exercise you do isn't strictly necessary.  Work out a reasonable average and stick with it. 

Thanks for replying :)

The trouble I'm having at the minute is making it up with healthy foods and not the more appealing chocolaty snacks :D but I am keeping to between 1300 and 1500 (so not 100% restricting to 1300). I am noticing a lot of fluid weight but I'm thinking that's due to what I'm eating as snacks (the meals I have are pretty healthy). I will definitely be endeavouring to change over the foods I eat, taking it one day at a time :)

To be honest about four days out of the week I do get a 20-30 min walk but other than that I mostly sit in mine or my boyfriend's room on my laptop or reading - we're both web design students ;)

Thanks for the informative and helpful post - it's really helped clear things up :)