What Commitizen type should I use for a change that is an improvemant for an existing feature?

Here are the Commitizen types:

What Commitizen type should I use for a change that is an improvement for an existing feature?

CZ resources :

• http://commitizen.github.io/cz-cli/
• https://github.com/commitizen/cz-cli

This has been discussed on Github. To quote one of the contributors:

In my interpretation, feat could include updates to an existing feature (new features for that feature). We could consider changing its description, if that would help.

From the available options feat makes the most sense to me too.