Hello Franz,
This is the “Quantity Discounts” feature which allows you to display quantity discounts on your single product pages. To use this feature, please go to the Dashboard >> XSTORE >> Sales Booster >> Quantity Discounts, and activate it.
For more information about this feature, please refer to our theme documentation here: https://xstore.helpscoutdocs.com/article/156-how-to-setup-booster-sales-quantity-discounts
Best Regards,
8Theme’s Team