What directory is cleaned when 'sudo apt autoclean' is executed?

If the following sequence of commands is executed:

sudo apt update
sudo du -sh /var/cache/apt

it shows 92M - of course for this current point of time. It could be other value.

If the following sequence of commands is executed:

sudo apt autoclean
sudo du -sh /var/cache/apt

it still shows 92M

Finally, if the following sequence of commands is executed:

sudo apt clean
sudo du -sh /var/cache/apt

it shows 28K - so is clear that sudo apt clean cleans the /var/cache/apt directory

Note for either sudo apt autoclean or sudo apt clean there is no output/result, but according with some tutorials the target directory used for cleaning purposes is /var/cache/apt, but ...

Question:

• What directory is cleaned when sudo apt autoclean is executed?