UFW – What does "rule changed after normalization" mean?

I give the following:

# ufw allow from 

And get the answer:

WARN: Rule changed after normalization
Rule added (v6)

I know the term "normalization" in relational database structuring, but I'm curious to see how it applies to the UFW rules. The rule I requested will then be listed as I typed it

Anywhere (v6)              ALLOW IN    

What happened in this normalization process?