Your Basal Metabolic Rate (BMR) is a measure of how much your body burns at rest. Another way to think of it is your base metabolic rate. A note of caution about the BMR calculators: they will only give you an average estimate. It's OK to use if you are sedentary with average muscle mass, but if you have been inactive for a long time and have a protein deficient diet it will estimate high. On the other hand if you are very active and have higher than average muscle mass the calculator will estimate low. The best way to know for sure is to be tested (which can be done at most gyms or your doctor's office).
How much an exercise burns is also a factor of your VO2 and heart rate at the moment. In general the higher the heart rate the more sugar you burn while the lower your heart rate the more fat you burn. Your calories burned reported by your treadmills and such are based on people with average muscle mass and cardiovascular health. Your actual values may be slightly higher or lower. For fun you can use a calculator like this one which uses your weight to figure out the calories burned. While not completely accurate, you will get close enough to plan your dietary needs.
5-7 pounds really isn't that much. In fact your body can fluctuate that much weight easily based on water retention, how much food is still in your stomach undigested, and whether you are constipated or not. Drinking lots of water will help with excess water retention, and cutting the salt intake down will also help in that area (you need some salt, but probably not as much as you are consuming now). Food digests when it digests, but many times people freak out after a large meal and swear they've gained 2-3 pounds. If gaining one pound of fat is 3500 calories, to gain 2 pounds of fat you need to eat 7000 calories more than your BMR--most people can't eat that much if they tried. It's probably the combination of the items listed above.
If you cut the carbs to only breakfast and/or dinner (none at lunch or a night snack) you'll probably shed those pounds pretty quickly. That's without calorie counting.
For me, walking 4 mph burns about 411 calories per hour. If you walked at the same pace daily for one hour without changing your diet at all, you would be able to lose a pound every 8.5 days. Adjusting the diet will make that quicker.