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/
That's only partly correct.
Write out the name for 50 and it becomes "halv tre sinds tyve", where "sinds" is a old word for multiply. Thus making a complete translation "half three times twenty" https://sproget.dk/sprogviden/spoergsmaal-og-svar/dansk-sprognaevn/sv00000047/