440
xkcd #3114: Building a Fire
(imgs.xkcd.com)
Title text:
That was quicker than usual! The cabin's sprinkler system often makes it really hard to keep anything lit.
Transcript:
Transcript will show once it’s been added to explainxkcd.com
Source: https://xkcd.com/3114/
The cabin is already on fire in panel 4. It is clear what happened. Then the words explain the joke.
It’s a typical instruction delivery speech structure:
Hence the text in panel 4 completes the pattern.
The point isn't it is on fire. The point is the roundabout way of getting it to be on fire.