Okay, I somehow lost 15 pounds these last two months, but whenever I try to work out the numbers, it just doesn't add up.

15 / 2 = 7.5 lb/month
7.5 / 4 = 1.875 lb/week
1.875 / 7 = 0.2679 lb/day or (if 3500 cal = 1 lb) 937.5 cal/day

I only lose about 250 cal/day.

Can anyone explain?

Because calories are a measure of energy, not weight. 250cals a day is the amount that your body burned off, once it had used what it needed. For instance, if you were eating 1500 and your body is used to 1750, then your body's normal metabolic rate would have to compensate for the loss of 250 cals by burning body fat/muscle tissue instead.
At least i hope this is right. I have half a science degree at the moment, but if i'm talking crap, someone tell me, cos i don't know too much about calories.

What do you mean when you say you only lose 250 cal/day? 250 cal from what?

Assuming you are losing fat and not water, your own numbers are saying that you are creating a 937.5 cal deficit per day. So, each day your body is getting that much less than it needs to maintain the status quo.

Not sure where you are getting the 250 from.

What do you estimate your daily caloric intake to be?

more than half ur body weight is water... so i asume when u burn 250 extra cals in a workout that would be about about 27g of fat, and some 30 grams of water if not more during the workout alone.. so lets say u permanently lose 60g of weight per day only during that workout

60g*60 days = about 8 pounds of fat and water permanently just during ur workout...

from metabolism increase during the day since u now have a more active life... you may have lost an extra 3 pounds of fat and water... so far 11 lbs lost...

less water retention due to lower carbs and reduced intestine content makes the remaining 4 lbs...

That makes sense, thanks.

lol don't question it...15 pounds in two months is sweet!!