500 calories per day is the average amount of extra calories required while breastfeeding. This is only a guide, therefore following your body's hunger cues is a good idea, as not all women will need this much.
Remember that if you've gained a healthy amount of weight during pregnancy, part of that is fat stores to supply the energy for breastfeeding. So your body has already planned for some of the extra calories needed.
The best option if you do feel an increase in appetite, is to simply increase the amount of the foods you are eating within the plan.  
Often breastfeeding woman are more thirsty than usual. Don’t ignore the thirst. It’s a good idea to have a water bottle with you, and perhaps get into the habit of always having a glass of water when you feed your baby.