Wow, 1500 is dengerously low. I did a very low carb when it was all the rage, and before I found this site. I ate about 1500 cals mostly protein, like 30 grams of carbs a day. I lost 15 lbs in 2 weeks, like 3lbs the next 6 weeks. Half the loss was muscle.
I have found that I burn 3,500 cals with just lifting 3-4 days a week, with hardly any activity, at a bodyweight of 225 @ 15%. I am sure that if you lift and walk around any at work, you are close to burning 3,500 at 255 lbs and 16%. The calculator does not figure in your daily activities. A moderately active person, lifting heavy 4 times a week and walking for hours at work, you can take that times 1.5.
I hate to see people just pick a number and shoot for it. That is what I used to do before this site. Get a fitday acount to keep track of your daily food intake. You can customize your foods to exactly what the label says. It can save the info for you, so when you eat that food, you can click it and add to your daily totals.
You will be surprised how many cals you burn a day. I have been trying to gain at 4000 cals a day. I just lift and walk around the dept store I work in. After 8 weeks I hadn't gained anything. I upped my cals to 4500 and am slowly gaining. Don't be surprised if you burn close to what I burn. At 255 and 16% you are bigger than I am. I do not have high metabolism and float around 15% year round.