Any time you see a four-digit number, you should try it as a Paige Code. Here are a few clues below.
For instance, in the group chat of Day 16, a certain someone gives the MC a specific rating...
In the Lexi flashback on Day 15, Paige asks the MC what time is displayed on his watch.
She also talks about her PIN number during the Tiffany/Raegan threesome.
Leetspeak.