Well do you have a longer commitment that you've been doing for a while? Lots of people have multiple activities, some which are far smaller commitments than others. This shouldn't look bad as long as you have something that you've been doing since early in your undergrad and have accumulated over 150+ hours. If this is all the volunteering or other stuff that you have, then you might be in trouble. If possible, quit these activities just after submitting AMCAS, since you could label them as being "current." But I'm assuming that's not possible. Good luck!