If you want to give a discount based on the quantity of the products your customer purchases, you can use the 'Discount' tab in Product to do so.
This can also be set to restrict the bulk purchase discount for certain customer groups only, like Wholesaler.
To access this, go to Catalog > Product > Edit > Discount
The Discount Tab needs the following information to include a discount for a product:
Customer Group: A group of customers (made in Sales > Customers > Groups) that meet the criteria to use this discount.
Quantity: The limit for the amount of products that can apply this discount.
Priority: Adding a priority number such as 1, 2, or 3, will determine when this discount will be used when other discounts are applied to a customer's order. 1 will apply this discount first, while 2 will apply it second, and so on.
Price: The discounted price.
Date Start: The first date the discount will be applied.
Date End: The last date available for use of the discount; the date the discount will end.
Once you've done this, the product description will show the discount criteria.
Like the screenshot below, it shows 5 or more RM6, while the original is RM6.20