Calorie defecit - do I have to account for EVERY consumed calorie?

I've been working hard on counting calories, keeping them below 1200 a day from what was no doubt above 3500 a day. I've also been working hard exercising and can totally see I've lost my double chin. I've been at 240 since about Christmas (even eating incredibly poorly and largely o_O) and decided to start taking the weight off about 2 weeks ago, but I haven't lost any numerical weight yet.

Do I have to burn off all 1200 every day with exercise to effectively lose the pounds?