i can not understand how i have just 15mb free of 300mb. everytime when i try to install an app, i get the msg "please delete some photos or videos to free up space". but i have only 7 photos and no videos. by the way, can the app "finder" delete files? i tried to delete some apps like stocks,appollo..vs but i cant. and which folders or files should be deleted to free up some space?