Look at the dog, not at the bag for information on how much to feed. Leaving food out all day will make it harder to house train them as their system is constantly at work.
If you feed him 4 times a day he'll be fine.
Deja, GSD, sable WL, female, born 11 / 2013
Cam, Rough Collie, sable, male, born 8/2015