It’s hard to say with the description given. Custom fields in ACF are always in a field group and they are related to some WP object, like a post type, taxonomy, user, etc. You can create options pages with ACF Pro https://www.advancedcustomfields.com/resources/options-page/ and then add groups to it. These values are stored in the WP Options table and are not related to specific WP object https://codex.wordpress.org/Function_Reference/add_option.
