i'm not sure what other calculators you are using, but this www.sparkpeople.com/resource/calorie_calcu
is how spark figures your ranges. ultimately, you could probably lose about 2-3lbs per week for the next 50lbs or so if you wanted, which would mean a lower range for you. if you are fine with losing slower, say 1lb per week, your ranges will be higher. if your by hand math isn't matching your spark ranges, then you need to go to your start page, look under goals and progress and adjust those things in there that are off [calories burned and weight progress are the ones you need to make sure have accurate info for where you are now]. once you have changed and saved those, the number should match up. i can't say where they would be relative to your other calculation, but it could be that that particular calculation has a slower rate of loss or takes into account your exercise [and you didn't have your calories burned number accurate on spark].
ultimately with where you are now, anything that you eat that's under what it takes to maintain your weight should result in a loss, so you have quite a bit of wiggle room if you'd like to use it.