Question about 10 days of time off for Vista volunteers

Hi guys. I'm planning on applying to Vista positions and noticed that volunteers get 10 personal days off. Do you have to serve for a certain amount of time before these can be used? Most positions start at the end of August and I entered the lottery for the NYC Marathon in early November. If I get a spot in the race I'd take a Friday-Monday long weekend. Would I not be able to take days off that early in my service if I let my supervisors/interviewers know ahead of time? Thanks for your help.