The difference is that for the ECA section you are only saying what activities you participated in. However, for the Resume section on the ECA's the prompt is:
1. Leadership and Extracurricular Activities: Describe all leadership positions you have held and extracurricular activities you were involved in to include athletic activities. Please include activities or leadership positions held during college and/or while enlisted. Briefly describe the impact you had within each activity/position. Please list these items in bulleted format and be sure to include specific grades/years of involvement and length of time committed to each activity.
So you should be describing the activities you listed in the ECA section in detail. What you did, how much money you raised, how you competed, how often you went etc.