Neither the Microsoft Band nor its associated Microsoft Health make personal recommendations for setting goals for daily steps or daily caloric intake. For that you need to do a little research and also determine what your overall health goal will be. Do you want to lose weight or maintain weight? Do you want to move more or just improve your activity?
Activity and diet go hand-in-hand. If you're trying to lose weight, you should aim to burn 600 more calories than you take in through food and drink every day, while the number of calories you should eat to lose weight depends on how many calories you burn daily.
The Microsoft Band comes with goal defaults of 5,000 steps and 1,200 calories per day. These need to be adjusted according to your age, gender, weight, height, and activity level. A person weighing 155lbs (70kg) can burn about 440 calories by walking 10,000 steps briskly (3.5mph). Here's a Calorie Calculator to get started with your goal setting.
Changing the Microsoft Band defaults is not a glaringly evident task. Altering the daily goals needs to be done directly in the Microsoft Health app installed on your smartphone. Once you have the main Health app screen showing, tap on either the Steps or Calories tile and then once inside the specific area locate and tap the Pencil (edit) icon. This takes you to the goal modification screen where you can adjust it to a more personalized setting.