It's usually related to school experiences that aren't within a pharmacy (research, case conferences, health fairs, and whatnot). At least 900 hours have to be within a pharmacy, but if you can do all 1500 from work you're fine. You can have 0 hours in the non-pharmacy category and be a-okay. At our school, the experiential coordinator would sign off on the 600 hours for students that couldn't reach the 1500 on their own.