Google Directions API limit

i am trying to draw the route between two markers on my google map which i implement in my android app. I have read, the way to do this is invoking the Directions API service. The Usage Limits says you could only make 2500 request per day, i am confuse about that, this limit will apply for my whole app traffic (all the users would be able to made 2500 total request) or apply for individual mobile devices (a single app instance running on a single device would be able to make 2500 request per day). I have found many questions about this topic but none official answer. I appreciate any help Thanks.