Can you explain why when you have 2 days of supplies going into Night 14, you find 2 days of supplies on day 15, and you end up with 5 days of supplies? 2 + 2 =/= 5 or am I missing something?

@ 4:21 you have 2 days of supplies at the end of Day 14. @ 5:36 you gather 2 days of supplies and the game indicates you have 5 days of supplies.

Is this a glitch, or expected behavior that I'm not familiar with?