Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
Check out my other builds too! As Garen you are a tank, but you can also kill. Garen if you've read his passive has insane hp regen. This comes in handy so much. Also, try not to take all the kills as Garen because you want your carry characters to be fed more than you. All you need is to take the hits like a good tank.