Hey, @Ihor-Sh
At this time, this is expected behavior for how our app displays bundles at the checkout page. Due to our checkout security settings, the checkout has limited customizations that can be done which wouldn’t allow you from altering how this app displays the bundle.
As @Ihor-Sh mentioned above, using Checkout Extensibility (Shopify Plus feature) would offer a solution to this.
If there is anything else I can help you with, please let me know.