Day Thirty Three

 is a part of the story in Firewatch.

Guide
Once the conversation is over, head north to retrieve your supplies. Use the map to find your way around, and get to Cache 241. Here, you can get more map information, as well as a few sundries.

Go towards the Supply Drop and collect the goods. You can grab more than just the Two Forks stuff, but you can also just grab the Two Forks supply and head back to the lookout.

After this, one of two things can happen: 1. If you grabbed just the Two Forks supply box, the placard for Day Sixty Four will pop up. 2. However, if you decide to grab the food intended for the other lookouts, the placard for Day Thirty Four will show up.