I would just enter the number of hours I typically devoted to those activities in one week. If you volunteered at Relay for Life once a week for two hours, enter two hours, even if you only volunteered once a month. Schools don't tally the number of hours of extra curricular activities. If they want more information, they can ask you. If you're not sure how many hours to enter, just enter 1 or 2, or something realistic.
Kevin
