Within Core-portal basic, you can filter on different product categories per product group in the sidebar. By default, you will see how many items are linked to each category. These numbers are highlighted in yellow in the image below for illustration purposes.
If you want to hide the total count, you can activate the setting Hide the total count of products per filter in the sidebar & filter menu. This setting can be found in the CMS under Core-portal basic > Settings > Catalog tab.