Good boy combo is a collectible artifact that is found during the chapter "Jackson" in The Last of Us Part II.
Description[]
The good boy combo is a handwritten note from Mina—a former employee of the Greenplace Market in Jackson County, Wyoming—about some supplies she has secured in a safe for her friend Kristen. Mina tells her that she has left some medication for Kristen's back, and warns her not to sell or give away the pills. She also says the combination for the safe is the date her "good boy" was Employee of the Month. Using environmental clues, the player can solve for the combination: 07-20-13.
Location[]
This artifact can be found in a small office off the supermarket break room. After the squeeze-through into the break room, turn right and open the door to the office. The artifact will be on a desk to the right of the safe.
Content[]
Yo Kristen - left the real shit in the safe for you. Combo is the
date my good boy got Employee of the Month. Don't fucking
sell those or give them away. That's for your back, alright?
Feel better -- Mina