Are you talking about the standard WP custom field area? This automatically shows the last 30 or so custom fields used anywhere on the site. ACF creates these custom fields and they are associated with the field group that you created. This is normal. You should not get rid of them because that will break the operation of your field groups.
Welcome to the Advanced Custom Fields community forum.
Browse through ideas, snippets of code, questions and answers between fellow ACF users
2022 was a big year for Advanced Custom Fields, with more capabilities, a new generation of ACF Blocks, a refreshed UI, and a new home. Our year in review post looks at advancements we’ve made and offers a glimpse of the future. https://t.co/HahJUCcyH4