This option is configured on "Performance" page.
/admin/config/development/performance
https://git.drupalcode.org/project/drupal/blob/8.7.8/core/modules/system...
There is a couple UX issues with that widget.
1 . The number of options is limited. You are not allowed to set an arbitrary max-age value.
2 . The maximal allowed value is 1 day. Why is that? Drupal 8 has got tag-based cache system which is supposed to cache never-changing content forever.
Proposed solution:
Use number input time for this setting.