Title text:
Other numbers are largely unaffected, but anyone using '4' for their certificate key is urged to upgrade to '5'.
Transcript:
Transcript will show once it’s been added to explainxkcd.com
Source: https://xkcd.com/3314/
I guess if I say that 1 is baker's 0, and 2 is baker's baker's 0, then I've invented the baker's unary base.