From your Shopify admin, go to Online Store > Themes.
Find the theme that you want to edit and click Customize.
In the left-hand toolbar, click Theme settings.
Click the Sales notification.
Active: turn on/off this feature.
Pick a product collection: choose a collection to show the products.
Limit: the number of products will be shown.
Image size: the size to scale product image. Please refer to this guide about the image size syntax.
Minute from number and Minute to number: in sales notification, you will see a text like this "19 minutes ago". Number 19 is generated in a range [Minute from number, Minute to number].
The time to display(seconds): the time sales notifications block is displaying a product before it is hidden to show another product.
The waiting time to display(seconds): the time sales notifications block is being hidden before it's been visible to display the next product.
Hide on mobile: hide sales notifications on mobile.